Hello Sidewinder,
I put a Doug Nash (now Richmond) 5spd in my '70 Chevelle years ago. It has taken a beating and has never given me any trouble.
The install is easy, and the "under car" fit is great. Same bellhousing, same crossmember, same tranny mount, stock driveshaft & yoke (tranny has M22/Turbo 400 output shaft).
The shifter that comes with the 5spd does not come up in the center of the car, or console. You must cut the floor to fit the shifter, which ends up on the left side of the tranny tunnel, next to the driver's seat. Great shifting if you don't mind cutting the floor.
I wanted the stock console, so I sacraficed an old Hurst Competition Plus shifter for it's "L" shaped shifter stem bracket, and combined it with the 5spd shifter. I had the bracket cut to the 5spd shifter, and the L bracket welded in it's place. This modification placed the shifter stem in the center of the tunnel/console. Next I had to "lower" the entire shifter because it sat to high and was rubbing the bottom of my floor pan. I redrilled the shifter-to-tranny plate so it would be about 1 inch lower.
Lowering the shifter an inch does throw off it's rods a bit, so the shifter does not shift as "close" as it would in it's normal installed position. Even so, after my modifications, I adjusted my shifter, and have been powershifting it behind a 454 for 9 years. Not a problem.
On the Richmond web page, the 6spd looks very similar to the 5spd, so it should fit. 6spd has OD, but you have to pick out a 1st gear that makes sense. If you pick one that is too steep, the 6spd may turn into a 5spd because you will be starting off in 2nd gear all the time.
Good luck, Joe.
