I've just sold my blown 496ci and i want to start building another engine but i dunno yet with which cubic inches should i go with?

Im confused between the 509ci and 540ci and what i wanna do is a street/ strip machine with a hyd. Roller Camshaft and a comp. ratio 10.5:1 or 11:1
and a 200 shot of NOS.i dunno which camshaft should i get and which engine Block

any suggestions?