My best guess on traction belts would be 954-0280 (front) and 954-0370 for the rear. You will find over and over again to use the OEM belts only, which you should try to do for good reason. If it isn't possible, I could measure- but notes should be on the web. The deck is depending on what PTO system it has. Some 46" deck s had idler pulleys under the pan and engaged w/ a separate lever. Most older 46" decks on a 600 series would create belt tension as the deck was lowered. So, is there a separate engagement lever on yours? You could post the first two digits of the engine code # and that would give us a year.

Can you find a model number such as found in the link I posted?
Format such as 133L670G147

Here is a link that might be useful: I Posted

The MTD parts search tells me no records are found!

Hi tomplum
There is no separate engagement lever for the deck so I assume the tension was created by lowering the deck.
I'm going to try and see if OEM belts can be found locally, if not I'll ask you to measure for me. Thanks a million

When you search for parts, drop the 602 and you will get results. Best of luck!

Here is a link that might be useful: parts tree

The previous posts answered most of the issues, but I'll summarize so the OP has all the information in one place:

1) Engine to Deck Belt:
OEM 7540439 or 9540439; 5/8 x 60 or B57
OEM better but have successfully substituted aftermarket or FHP

2) Deck Belt, Blade to Blade:
OEM 7540440 or 9540440; 1/2 x 99 or A97
OEM better but have successfully substituted aftermarket or FHP

3) Engine to VS Pulley:
OEM 754028 or 9540280; 5/8 x 53 or B50
Only use OEM; This is the only one I would never substitute

4) VS Pulley to Transaxle:
OEM 7540370 or 9540730; 5/8 x 48 or B45
OEM preferable, but substitute can be used as long as it is Kevlar corded and has wrapped construction.

Just my two cents, but I would use aftermarket on the deck, and OEM on the power train, because the power train is often more difficult to remove and replace. The deck is much easier, so if you get shorter life, at least it's a 30 minute job vs. a couple of hours.

If you don't have the correct deck for the tractor, you could rig up a method of towing a mower deck behind the tractor. It would need a running engine on it. I did that with an old Craftsman lawn tractor, which didn't have the right deck on it, and i had no way of finding the right one. I also did it with a lawn tractor that had the correct operating deck on it. I made an off-set draw-bar to pull the extra mower deck, which i needed to mow an extra large lawn area. A bit of experimenting will enable you to figure out the correct design of the tow-bar! And the pattern to use when you mow!