Mostly it comes down to miles for me. The FRC was hitting just over 70K, and that meant eventually I was going to have to look at an engine rebuild and other maintenance issues as well as the 90K tune-up. And it becomes next to impossible to sell them for any amount of money once they hit 100K or more.
And right now prices on low mileage (>20K) C5 Z’s are in the low 20’s. Stock or slightly modded.
But if I can find a LS3 C6 in the mid to high 20’s, I will also consider that.