As this is a gravity feed unit, I need to place it higher than my tractor tank. My thought was to mount it on a sturdy shelf in my shed about 56" off the floor of the shed. My shed is about 150 feet from my house, in case you're wondering.

Assuming my tractor and other equipment are sitting on earth when being fueled, do I need to worry about grounding the metal storage tank? Also, are there thoughts on the need to clip a grounding cable from the tank to the frame of the tractor when fueling? Seems a good idea to me (like they do when fueling airplanes), but might be overkill. I just want to do what I can to avoid any regrettable incidents that might damage property or limb.

Thanks for the help!

Probably the best bet would be to drive a ground rod 8 feet into the soil outside the shed. Locate it into the soil at the drip end of the roof, or near where a downspout empties if there are gutters.
The ground rod does not need to be driven "straight down", it can be driven at a shallow angle. Dig a small hole about 1 foot in diameter and drive the rod inside the hole so that when you are finished driving, the end of the rod is below the soil surface.
Or you can dig a trench 8 feet long and 1 foot deep and simply lay the ground rod in the trench.
Connect a #4 solid copper ground wire to the rod using the "tear drop" style ground clamp and run the copper ground wire inside the shed by whatever means is convenient.
If it suits you to slip the ground wire under the bottom of your wall (if dirt floor) or make a small hole for the wire to enter.
The wire does not have to reach all the way to the storage drum, but it does need to terminate inside the building.
Once the ground wire is inside the building you can connect to it using 14 or 12 gauge stranded automotive wire.
A good way to make a sound connection point on the #4 ground wire is to use a #4 electrical eyelet terminal and solder that (rosin core solder only) directly to the end of the ground wire.
After you have the eyelet terminal in place, you can fabricate 2 grounding cables (one for the fuel storage tank, one for the machine to be fueled) with eyelet terminals and attach them to the ground wire eyelet. I suggest using stainless steel machine screws/bolts to do the attaching or use a generous amount of antiseize compound or electrical "No Co Rode" compound.
To attach the ground cable to the tank and the machine to be fueled you can simply fit the cables with alligator style clamps.
Leave the cable to the storage tank clipped in place all the time.
Connect the ground cable to the machine needing fuel before you do anything else when refueling.
You had better make it a habit to drape the cable for the machine across the seat or the ignition key switch before you clip it onto something or you will at some point drive off and at least mess up something about that cable.
That is why I do not recommend the machine ground cable to be run directly to the fuel storage tank, too much chance of you doing a "drive off" with a ground cable connecting the machine to the storage tank.
I consider it important to use 2 separate ground cables to serve the 2 functions.

The ground rod is a standard NEC approved grounding electrode. It and the teardrop clamp and #4 copper ground wire are available at any electrical supply house or a good home improvement store.
If you choose to do the trench method instead of drive rod method you cab substitute a 10 foot length of 1/2" copper water pipe for the 8 foot driven rod.
In this option you can flatten about 1" of the copper pipe and drill a 1/4" hole in it. Your 12 or 14 gauge ground cables can then be attached to this hole with eyelet terminals. Beware, the eyelets MUST be soldered to the ground cables (rosin core solder only) and stainless steel fasteners used to make the connection to the hole in water pipe. Additionally I suggest you paint the entire juncture of ground cables to pipe, including about 6" or so of each cable with liquid vinyl electrical compound.
Be sure to consider that the cables used this way may need to be given some protection from physical damage (weed eaters, lawn mowers too close, etc.) so you might want to drive a sturdy metal bar/rod into the ground so that the cables are behind the protector as they leave the trench and enter the shed.

If the shed is constructed of metal and is sitting atop a concrete slab (anchored to slab) you need only make 2 ground cables with alligator clips on one end of each cable (on all 4 ends if desired).
Use one ground cable to connect between the storage tank and the metal structure of the building. Use the other cable to connect between the metal building structure and the machine to be fueled.

I appreciate very much you taking the time to write out a description of what you would recommend. Immensely helpful. I'll report back on exactly what I do for posterity.

Lighting struck tree when down the tree and hit the metal rod blowing it out of the ground. Ok, that wasn't the bad part. For what I could figure out The lighting strike was directed down the tree, then the rod picked it up, blowing it out of the ground. Now the lighting didn't stop there directed by the buried rod. Beings there was buried underground cable about 2 1/2 feet near and below the rod laying sidways in the ground lighting continued through ground to the underground cable knocking out my master breaker box in my house. Luckily it didn't catch the house on fire and just blow out several breakers. I eventually had to have the main breaker box replaced due to the lighting strike.

I would just make sure nothing underground could create problem in case lighting struck and the grounding rod picked it up especially anything laying sideways underground.

Mownie - definitely understand that your suggestions are just that and not strictly NEC. I intend to follow NEC as it just avoids a lot of silliness in the event something goes wrong. I'm going to try driving the 8 foot rod in via hammer drill. Barring success at that, I will do the 2.5 foot deep trench. Connector will be rated for direct burial and the #6 wire (I'm using THHN) will be encased in Sched. 80 conduit from dirt into the shed structure. Better safe than sorry, which is the whole point of putting a ground in the first place. I'm amazed at how many people just throw a metal can on a shelf, siphon out and never think about this stuff. I'd rather rely on science than luck!

I used a direct burial connector and ran my #6 THHN from that into the shed (about two feet) within conduit. I'll make the connections next week and get that tank installed.