I installed a Tremec TKO 500 (TCET 4616) in my vette this spring and after running it a while I can honestly say they are worth the dough imo. I'll have one in the '58 someday.
It's a fairly straight forward swap that matches well with the chevy. Input shaft and bolt pattern are correct, so you can use a stock bell housing (on a V8, not sure about a 6). There are a wide range of shifter locations available. They also come with both a mechanical and electronic speedometer drive.
