Building my first-G or GM?

I've been looking around on here for a while and thought I mine as well ask a few questions!

I recently acquired a powerblock and pistons for a G with the intention of building a puller. I just want to have fun and clean house at a few local pulls which are dominated by Mini Moes.

So what would be better to start with, a G or a GM?

For the first year I just want to get the tractor going and then next year I would like to go even further.

So here is my plan to start with:

-Get rid of the cast centers and go with new BLANKS on the back. Should I go with 20.8's or 18.4's? I'm leaning more towards 18.4's but that is just my personal preference.

-Put in powerblock (of course )

-Pendex Ignition

-K&M air intake

-Murphy's manifold with 720/730 carb -or- just stick with a big nut carb, not sure.

-70 cam

-Balance crank and run 2500 RPM

-Head-it is worth it to run a flathead or should I just run it with the stock head for now and throw a Murphy's on next year?

-Take off powertrol.

This is what I have gather from talking with a couple of different guys around my area and abroad.

Is there anything out of line in my thinking and is are there anything else anyone can suggest?

I also have an A with a powerblock that I plan to do something similar to so I can pull in the 4750 class.

Thank You.

Sounds like a wild one. Everyone has there own opinion but the cam would need re worked and the head gone through to support those rpms and light pistons would be nice and so on. Give me a call much easier to talk on phone 9892775366

2500rpm is that doable? u better call josh before you start this project..lol. isnt a 70 cam pretty much same as a g cam?

(quoted from post at 15:49:15 04/18/11) Sounds like a wild one. Everyone has there own opinion but the cam would need re worked and the head gone through to support those rpms and light pistons would be nice and so on. Give me a call much easier to talk on phone 9892775366

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Thanks Josh I will be giving you a call.

(quoted from post at 18:08:34 04/18/11) 2500rpm is that doable? u better call josh before you start this project..lol. isnt a 70 cam pretty much same as a g cam?

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Yes it is, there is more than a few guys doing it around here.

2500 is a very easy number to reach with a G. and it will stay together.

70 gas is the same as late styled G cam, The big nut will supply enough fuel for that setup, will save you money on getting the 720 carb + the crazy price of the duplex manifold to g head. Use the cyclone head with your tractor - match port manifold to head, cut .250 off, blend in rough areas in IV bowls, relieve the eyebrow back a little the shrouds the IV, get a multi angle valve job. With no added stroke, even a 18.4 is a lot of tire, sounds like you are shooting for a 5500 lb class.

I've got a G I pull in div.1 and have plenty of fun pulling against tractors that are pretty much stock too....because they have to be to make the division. And while my G is "warmed up some", I can do anything with it, plow, pull, parade, run threshers and choppers...whatever...and for me, that's fun too. (And it still looks like a regular John Deere G.)
Anyhow, if you're gonna try to beat up on Molines...in whatever class they pull, you're in for an expensive experience. Molines like U's, 5 Stars and so on can mix and match parts from bigger engines in their engine family and get horsepower that is VERY difficult to get with a John Deere G unless you're ready to stroke it and get a bored and sleeved to the max. block and get the G's engine up to at least 7-800 cu. inches. Revving up and high compression only helps some...not enough to get the power to beat competitive Molines, or Olivers, or Farmalls in the high power divisions. You gotta have a much bigger engine to move enough fuel/air mixture and burn it to compete against big engines in other make tractors.
Oh, I might mention I've got a "regular" Moline U too...and have a lot of fun with that pulling against Farmalls, Olivers, Cases, Masseys and those green two-whoppers and that's enough for me.