I think a 4.125 crank like BPE sells at 4.100 bore should get you around 440 cubes.

If i was doing old school smallblock like that, i would probably use a 48 degree block and the 48 degree indy heads. good roller ,good headers, should be able to make 700 without a ton of effort.

could just as easily do it with a good X block at 4.100 bore as well with the 59 degree indy heads.Electric water pump, vacuum pump,electric fan, etc should be real doable.

Another way is to just by an r5p7 busch motor, run it on e85 and you are there as well, and WAY cheaper.