If your gonna build a full race engine and want to start with brand new parts to get the job done I found a great site that sells blocks, cams, rods and pistons to suit your B and D series engines. RS Machine
B Series Engine Archive
I found writeups on B Series and D Series honda engines on wikipedia and so far i got that B Series are more expensive to build then D Series but besides that it’s still hard to choose, ether the B16A 160HP or the D16Z6 125HP. Now the B16A has more HP but cost might be a problem. Time to do more research.