What manual valvebody for my 904?

I'll have to check mine. Its a mid-70s 904. Is it stamped on the lever, the ratio? How hard are they to change? I think the transmission will end up being my weak link, but for now, its all I have and can afford. Hopefully it suprises me though. Is there anything else I can do to it to help it last, and perform better? I may go pick it up today just to take the pan off and look at the lever.

The ratio is stamped on the side of the lever. Not too hard to change but you do have to remove the starter and dust cover to gain access to a pipe plug located in the bellhousing that holds it in. Have it rebuilt to high perf. specs, install the biggest trans. cooler you can get, install a upgraded input shaft, and install a top quality converter with a billet hub.