Determining need for high test fuel?

I have researched this a bit and think I am heading in the right direction but I would like to ask one of you Guru's about the need for high test fuel in my car.

I know the PO used high test but he also had more money than I do.

I should add that I have so far run a mix and I am noticing a bit of backfiring when backing off the throttle and some run on one occasion!

If someone could please let me know what information about my engine is needed to determine this I will gather it together and post it here.

I am thinking stuff like carburation (it is a 650 Edlebrock), heads, cam (it is a comp cam but I will have to find specs), etc...

Thanks in advance for any assistance you may be able to provide.