The biggest plus of most C3 chassis over the typical C2 is the rear kick-up gussets added during the '68 run. Geometry wise, replacing the C2 rear camber strut bracket with at least a C3 piece (if not VB&P's cool bracket) would reduce (you don't want to eliminate it except for drag racing) the excessive camber gain inherent in C2's. Any other improvements you might make to one are pretty much applicable to the other.
Also, the '80-'82 Dana 44 batwing diff isn't quite as strong as the earlier 10-bolt, which can be an issue with high perf engines. Good news is that the latter can be fitted with a little adapting work. Bad news is that 12-bolt IRS diffs evidently don't fit the batwing, should you ever want to go that route.
edit - The C3/D44 batwing can be adapted to accept a 12-bolt IRS diff with a spacer/mid-plate to make up for lack of material.
Last edited by TheSkunkWorks; 10-01-2011 at 10:44 PM.