400 low deck block, 4.375 bore, 4.25 stroke for 512 cubes. 2.200 chev rod journals on crank. 6.535 H beam rods using .990 pins. 1.32 compression height pistons with enough dish to keep compression where you need it. If you go E85, set it at 13/1 for use with a big cam.
There are two ways to go from here. Small port route for low rpm torque, or big port heads for max power. Indy SR small port heads flow very well, and can also be ported and opened up to max wedge to flow 355 cfm and still use standard offset valve gear. Going up to a 440-1 head allows for another 25 or so cfm and another 50 to 75 hp when max ported using the right cam, etc. The Indy heads have enough meat in them that they can be cut to 62cc if you need to. I have a 528 RB motor with 440-1 heads cut to 62 cc that is at 15.1/1 compression with a dome of only about .060 high.
Chosing a cam carb and intake system will be dictated by where you want the hp and torque, and budget.
For a moderate budget, all out hp build, this is what I would build-
SR heads cut to 62cc, max ported to max wedge port size. Set the heads up for Beehive springs, for the highest lift possible that those springs will handle.
Wiseco 1.32 compression height pistons, Manley 6.535 H beam rods, Ohiocrank crankshaft if they make the 4.25 stroke low deck crank.
Indy single plane intake for a small base holley
two inch Dominater adapter and a 1050 Dominater for the carb.
High ratio rockers, 1.7 preferred. 3/8 heavy wall pushrods.
Good quality lifters with the EDM hole in the center of the base for direct oiling.
Cam specs should be somewhere around 275 degrees duration at .050 on the intake, an additional six degrees on the exhaust. Lobe seperation will be dictated by the total duration to some degree, but most likely 108 or very close. Put it in at 106 to start, or grinders recomendation.
The 1.7 rockers are for getting almost roller cam performance out of a flat tappet.
The lobe design would be chosen for as much lift as the new design Beehive springs will allow. It is also important to make sure the rate of lift is for a .904 lifter to get the advantage this whole package is after.
If you want to upgrade to a roller cam, then set the spring installed height high with +.100 retainers and also +.050 locks if you need to. Shoot for 2.00 to allow over .800 lift. Better rocker arms are needed, along with thicker pushrods to handle the seat pressure that you will need. Again, use 1.7 rockers. Seat pressure can very some depending on which springs you use. If you go with a big triple like a comp 947 they install at 2.00 with 340 on the seat. Trust me, you need this much spring to run an aggressive roller cam. I picked up 40 hp switching from "enough spring" that had 225 on the seat to these monsters. There are better double race springs out there also that will fit the application. For an off the shelf cam I used an Isky RR735 for my 528 on the first dyno session. It made 847 hp with alky, and is not that big of a cam at 280/288/110 . To get the best out of this cam, a higher ratio rocker should be used on both sides. I had 1.55 Jesels on mine, but Isky said I could go to 1.65 ratio for .808 lift. They might even agree to 1.7, but you need to call them and check.
At this level of roller cam (aggressive +.800 lift) it is pushing the limits of the cam core size, and you will notice that the cam flexes as you rotate the motor to set lash! I see .003 in spots. Keep that in mind when you select intake valves. If there is a hollow stem steel intake valve available, I would install them. If not, a Titanium valve will help make more power because it will reduce deflection in the valve train and won't bounce as badly when it lands on the seat.
For the oiling system you will need at least a 9.5 quart pan and an external pickup to properly feed this animal. For safetys sake, use good 20w50 RACE oil. Set the oil pressure from 65 to 75 psi max.
Headers can be 2 or 2 1/8 inch by 32 long with 3.5 inch to four inch collecters. It would be best to run the PIPEMAX program to pick out the header sizes.
Rpm range will be about 6800 to 7,000 shift points. This combo should make somewhere between 725 and 750 hp and still be relatively cheap(if that is possible!) to build.
I have run the Mopar 590 cam using L88 chev springs with 1.75 rockers on a stroker in the past, up to 6,000 rpm. The lift with that deal was a theoretical .688, or .662 after lash. The new Beehive springs are said to extend that range 1,000 rpm with the same or less seat pressure. When the cam is chosen, be sure the guy that you talk to to select the cam wants to run a fast, high lift exhaust lobe. That has proven to work much better than the low lift long duration lobes that were the rage in the past.