What size is the current bore?
On your deal I would look at buying and using a 4.25 billet steel center counter weighted crankshaft(check with Ohio Crankshaft for a good deal on them ) with either BB Chevy 2.2 or large journal SB Chevy 2.100 rod journal sizes and good set of rods, steel or aluminum and then the best custom pistosn you can get with .043,.043, 1/16 oil rings set up for a vacuum pump, no gapless rings
The B1 heads and top end parts you have now will rev to 8500 RPM pretty easily with all the other good proper parts to do that, if your willing to do that then buy the good parts now while every thing is still in good shape
I have a new high nickel cast iron 4.500 bore size Koleno block and a set of B1-MC heads with Ti intake valves that I am planning on building a 555 C.I. bracket motor with a old used Sonny Bryant top fuel forged steel fully counter weight 4.375 stroke crankshaft with BB Chevy rod journal sizes and all new parts to achieve near 1000 HP on E85 fuel with a single large dominator carb., or maybe two 1050 CFM Dominator carbs on a sheet metal tunnel ram on E85 if needed