You have only found the EPA emissions ID decal.
You need to be searching for a decal stuck on a valve cover, or perhaps a metal tag riveted to the engine with numbers engraved on it. The numbers you need are: Model number, Type number. Serial number not necessary.
The engine "model number" on the EPA sticker is not a valid Briggs & Stratton modele number.
How about you post the Sears 917.xxxxxx number from under the tracor seat. Sometimes Sears has a good owner's manual online that actually has the Briggs model # and type # listed in the manual.
And some Sears manuals are garbage grade junk providing little useful data for the owner except the second half of those junk manual do let you practice Espanol.
Staying with a Briggs engine will make it easy enough to assure the alternator output is good enough for your tractor's needs because the alternator stators will interchange with most Briggs (in a class or series) so your old stuff can just be swapped to the next engine if required.
Once we determine the identity of the engine for sure, we can see about getting you some manuals and IPLs.

According to the OM it's-

445777-0154-E1

thks fellas....went back over it today...still no sign of the number...so thks to Bill for providing....

I saw the same engine referenced on another thread....so I know which "types" to look out for....odds are I'll have to use a different size engine tho...there don't seem to be many 25 hps around.

Question though...I bought the mower from a guy for 100 bucks--the previous owner said this about the engine ....it was knocking..so I shut it down.....my Dad came over and I cranked it up...he listened to it and said I was about to spend major bucks....get what you can for it. So it sat up for 5 years and he finally got around to selling it when he divorced.......it has 230 hours on it.

If it runs but has a knock..it this indicative of bad valves? connecting rod issue?

Could it be worth tearing down and repairing?

Don't be so concerned about getting "exactly" 25HP. Many times, the only difference between engines is the HP decal.

The main concern is to make sure you have the same type, ie V twin OHV etc. and the PTO stub dimensions are the same.

The charging system can probably be swapped over from old to new, IF necessary.

You can download the individual IPL's from Briggs to compare the part#'s of the stator & flywheel.
Chances are you'll find the same crank shaft, pistons etc.are used in both. (PS if your crankshaft PN's match, the PTO stub has to be the same dimensions.)