6. ZL1 1Le. I would do pulley and headers maybe H/C
Pro: Light mods make this into track monster that will outdo 350 in every way.
Con: Its a camaro. Also would spend most of its life on street which seems like a waste.
I have driven most of the cars you have on your list on a road course(Mosport)
I would pick up either the ZL1 1LE or the GT350 and the only upgrade you need to make is switching the brake fluid to Endless RF650 or Castrol SRF. You don't need any further modifications to either of these cars to make it a track monster as they already are fast as hell. Furthermore, instead of modifying it further, I would try and find local HPDEs and get as much seat time as possible (with instruction). You will probably not exceed the car's limit for quite some time. Instead of mods, just buy extra sets of tires and brake pads.