If it were me (just my opinion) I would steer away from that type of transmission. Mainly from an original-looking stand point. That long, truck shifter will look kinda funny comming out of the center of your floor hump. It might also be a little too far forward and hit the dash. A friend of mine put an S-10 5-speed in his 58 and the shifter just looks out of place.
I went down this road before and I've looked at the options:
From my measurements a gear vendors won't work. Not enough room behind the trans.
There's the tremec 5 speed. Pretty expensive and you have to modify the trans tunnel quite a bit.
There is the OD gear sets for the muncie 4-speed. I believe PVS409 has one. Wayne Euper built it for him. Less expensive than the 5-speed and you can use existing bellhousing and shifter. No mods to floor. I believe you need a trans with a 1" countershaft for the gears to work.
What I did: I found an NP440 trans from an early 80s full size chevy pick up. Same length as a muncie, mount is in the same spot, all aluminum, same gear ratios as a 700R4 (3.06, 1.56, 1.0, .73), uses external shifter linkage. I had to get a truck bellhousing (trans has larger bearing retainer) and a block-mount starter, if you don't already have one. Here is a link to the thread I posted about my swap.
http://www.348-409.com/forum/showthread.php?t=10297
Best of luck!!
Ross
I did a couple of searches and didn't find anything, so if this has been posted before, guide me forward !!! 
