I have GSC 272's ( non S series ) and want to upgrade springs and retainers to rev more. Are these cams going to be able to handle an 8000 to 8500 rpm rev or is it time to upgrade?

 

they will do fine. cams and rpms dont matter.
its springs and retainers, so you dont float a valve,
and you stock rods can only spin so fast,...

throw some springs/retainers, i got mine from buschur, and tune it to spin to 8-8,500 and youll be fine

 

are springs and retainers hard to do yourself?

 

It's not so much the rods as the rod bolts. The upward swing when there is no compression (exhaust stroke) is the killer.

But with upgraded springs/retainers I agree on the 8500 RPM limit with a stock bottom end.

 

I rev mine to 8500 with FP beehive springs. They do NOT require upgraded retainers. I did my install with the head still in the car. It was a pita but much cheaper and faster than pulling the head and doing it on a bench.