164 tooth b/h wont change the length it will just make firewall to bellhousing clearance issues, u will have to beat the lip back with a bfh, cut it off and beat a little bit, or 3" body lift. 157 tooth flywheel will clear, just have valve cover to hearter box clearance issues. just heat up real good with a heat gun and use a ph8 style oil filter to push it back sone. its prolyepylene(sp?) or something like that. real easy to bend once heated. the c5 with a 157 tooth b/h and flexplate is the way to go. or u can buy a c4 aftermarket(PA, tci, b&m, or used) and do the c5 tailhousing and output shaft swap. personally, when it comes time for me to swap in my 347 in im goin c5, alot easier, less work, and around here parts are easier to find for the small b/h
EDIT: with the c5 u will have to move your tranny xmember forwards a little bit(most holes are already there, i think u have to drill 2 i can remember), and your front dshaft will need to be shortened 2" and rear lengthened 2" no biggie most b2's have the crappy gkn that needs to be ditched anyways