I put a gear drive in my 350. I got it from Summit. At 3000miles the idler gear let go and pieces went through my engine. The gear lost pieces of a few teeth.
I really do not like the gear drive. Not for the teeth coming apart but the noise and vibration. I put it in a van! Loud or what!
My rebuild has a double roller Cloyes now. I suspect I could never get my engine tuned to the point where the difference between a chain and gear are even measureable. It was fun for a few minutes, and then it was a little overbearing.
Go with a chain. It works.