2. Mower. Which one is best? THE CHEAP ONES! In the IMOW class, the mowers are all pretty similar. Get the mower you have sitting around doing nothing with. They must be Full Stamped Steel Frames. A good cheap mower to look for would be something like a, craftsman, dynamark, murray, etc.
3. Stripping. Strip the mower of everything you dont need. All the deck mounting hardware, extra bolts, etc. Then clean it all, this will make it alot easier later.
4. Transaxle (rearend). Find yourself transaxle if you dont already have one. There are really two types you can use here. If you dont mind the H-pattern 3 speeds, then they will work good. Or you can use a peerless straight shift trans, these are a dime a dozen.
4b. Transaxle Final Drive. You must figure out now what the drive ratio of the transaxle is. There is a couple of ways to do this. First if the transaxle is still in the mower, just push it across the floor one complete tire revolution. While it is going count the revolutions of the pulley. This is your Transaxle ratio. If the Transaxle is out of the mower, get a buddy. Have one person hold one whell while you turn the other. Turn it one complete revolution while counting the times the pulley gos around. Then divide it in half. This is your Transaxle ratio. Note: chances are if its a 3 speed H-pattern style it will be 9-1 and if its a straight shift it will be 12-1, however there are exceptions so check.
5. Motor. Your need a single cylinder, non-overhead valve 15hp or below motor. Get one that starts easy and runs well. Make sure to clean up that carb, or mark my words you will have problems
6. Pulleys. These are what will get you your final drive. If your rearend was a 9-1 then you have it easy here. You can use whatever pulleys you want, as long as they are the same size front and rear. If your rearend was 12-1 you will need to use a, 6" front and a 4 1/2" rear. Or a 4" front and a 3" rear. There are others but these are the easiest. And make sure to use belt gaurds to keep these belts on when the clutch is in.
7. Brakes. In Imow, stock brakes will usually work ok. I like to put a big spring on the brake arm to keep it from sticking on. This will make you very slow if they stick.
8. All the other stuff.
Kill Switch. Get a tethered kill switch and mount it before you do anything. You can get one at Napa or any boat/atv shop. Hook it up by connecting one end to the kill wire on the engine, and the other to a good ground.
Throttle. Get a bike brake grip and mount it on the steering wheel. Now get a throttle cable for a go-cart, motorcycle, or anything else that moves freely. Mount the cable to the handle. The other end can be run straight off the govener, but if your not real familiar with this, just run it to where the original throttle cable went. Then put a spring to close the throttle when you let off.
Steering. This is a biggie. You need to take the slack out of the steering somehow. If your mower has those cheap tie rods with no ball type sockets on them, CHANGE THEM! Do whatever you need to, to get the slack out of the steering. Try New parts, shims, tightning stuff, or welding the front axle.
Deck. Just find an old deck, cut it to fit under the running boards and bolt it up.
Tires. I like to fun tubes in these, you dont have to though. Tire size is limited so just find a matching set that is the right size. Turf savers are usually this size and easy to find. I like a set made by goodyear.