I've had good experiences with Hurst Driveline with my switch from an auto on my '68, both from the sales side and technical support. I have a 383 SBC and had to cut the transmission tunnel in order to raise the T56 enough to get the proper driveline angles, but not sure if that was due to my Morrison frame or SBC mounting height. Hurst gives a Lat-g discount so be sure to mention. I ended up getting a pre-fab Speedtech trans tunnel cover b/c I wanted to keep the stock center console:
http://www.speedtechperformance.com/...rod/prd264.htm