engine/trans compatability???

okay, im going to be building a Caterham kit in the very near future... im ordering it in a couple weeks.... im trying to line up the power plant for it and i've decided that im gonna go with a chevy small block- either a 327 or 350, whichever I can fit in the the engine compartment w/o many modifications at all..... what i need to know is does that limit me on the trans that i can use, cause i found a Tremec trans for a good price but from what i know about them it's a transmission for a ford mustang.

I guess what im getting at is with a chevy small block what transmissions are compatable and also in that which would be the best. I'd LOVE a close ratio six-speed but i know that i might have to settle for a five-speed. The other thing is that i'm looking to not spend an arm and a leg..... if i was i'd get a six-speed from caterham for $7,000. If anybody can help me i'd really appriciate it. Transmissions were never really my thing and i don't know all the specifics and the ins and outs of what will link up with what. Thanks in advance.