I am building a sb for a mud truck. I am using Iron eagle heads with 215cc intake runners. I have two options for blocks. 350 4bolt or 400 2bolt. I am on a limited budget so splayed caps and line bore is out of the question. I am leaning towards the 383 with Scat crank and 6inch rods int balance. I will fill the block up to the freeze plugs. Flat top piston. Solid lifter possibly roller if I swing the funds. Would the 400 be worth while? Any luck with 3.8?? stroke. I am looking for a good 500hp without spending a fortune. Thanks, CB

Normally I'm a 400 man but knowing how you animals with your mud boggers like to use your tach needles like a fan :D and not having the budget for aftermarket caps I would stick with the 383 and the 4 bolt block. If this is race only fill it up to the bottom of the waterpump holes and clearance the pistons an extra .001". You have the right idea with the Scat crank and 6" rods, go with the Mahle powerpak pistons, they come with a decent thin ring pack and don't require oil ring support rails, and they are bloody light. Light enough that I think a STD weight 5.7 rod could internal balance a bunch easier than working with the 6" rod model. May as well go with the 7/16" Scat I beam rods for the extra strength and better cam clearance while you're at it.

Is this for fun on the weekends or racing ?
If you're going to be low speeds... either 383 or 406 will do (the 2 bolt 400 is said to be stronger than the 4 bolt in stock form) and you'll be wanting low end torque... the 215 heads will hurt that Vs. a 190/195.
As for 400's and rpms... not an issue here (7000rpm 406) just not every weekend and held there over long periods of time.

Racing- build it like a drag motor, gear right, and keep wheel speed up.