Thats a question that always gets a lot of different answers. Ive always been told that 10-1 is about as hi as you should try without having problems, but some say 10.5-1, 9.5-1, its always different.
I had a sbc that I ran 10.25-1 and with 94 octane it ran OK, but with much under 90 octane would just start to ping when pushed hard.
With alluminum heads or a hi lift cam you can run the comp a little higher, but 10-1 is real close to the max on pump gas. HG