426 pistons

Hurt ?? Not sure what you mean by that. There are 426's out there in the pulling world with 4 7/8" pistons in them.  You can't expect the engine to provide the hrs of service that it would achieve with OEM size components and you sure wouldn't farm with them, would you ???

Where would you find some sleeves and pistons that are 4.75.

Seems like 5020 Deere pistons can be made to do what you want. Like Mack says, Darton sleeves or L.A. Sleeves.

Counterbalanced crank better?? Yes.  Necessary ?? Nope. Steel main caps ??  Girdle ??  Depends on how much HP/size or turbo you intend to run. Open RPM ??  You're not telling us much...……….

I know Dr Allis but my 91 year old dad always told me you don't even tell your best your friend you're going to whip someone after they sucker punch because your best friend will tell someone and someone else and before you know it the guy that sucker punched you knows you're coming (so to speak).

So with all that said I don't want the most cubes or the most HP simply because in my opinion you don't always need the most to win as over the years you always see the green guys making mistakes during their run and they can be beat.

Now my pump has been worked on by scheids diesel and runs great in a no speed limit class which about the time I quit because I pulled the guts out of the motor and it finally pushed the valve cover cap off during a run and covered me with very hot oil so it's been sitting for many years.

However it isn't set up right for speed limit classes in my opinion and would need reworked for speed limit classes,i ran a switzer to4 turbo and a few other things have been done.

I now have a 3700 MK II motor for it that is in shop being hot tanked along with checking the crank,cam and the head.I just thought maybe some 4.5 pistons not 4.75 as I mentioned would give it some more grunt in speed classes and I would still be able to pull my rolling plow with it and not burn it up.

Sorry to be so long.

But here at home the green guys will try anything to keep me off the track in stock classes.

Well, spending a lot of $$$$$ to make more cubic inches to still be able to farm with it and the main reason (to begin with) was to do well at the County Fair is a new one on me.  "Speed Limit" classes is still very vague. There is a huge difference between a 10 MPH class and a 12 MPH class. There are even some organizations that have 15 MPH classes.  While the engine size is important, the proper turbo/injection pump (not always a Roosa)/ injectors and GEARING are more important than just cubic inches. If you don't have a gear that lets you come down the track just on top of the (proper size) turbo and then throttle up the farther you come, you're not going to do very well.  Your 210 tractor has a perfect gear for 10 MPH and even at 12 MPH 6th gear isn't too bad. This is assuming you are limited to 3,000 RPM, which you don't say.