A833

For the hydraulic clutch: http://www.forabodiesonly.com/mopar/showthread.php?t=33640

I don't think a 5 speed would be an easier setup. Custom trans mount and driveshaft would be needed among other things. Plenty of places sell humps. Year One, Paddock, Goodmark, AMD, etc.

There are 2 types of regular (4th gear is 1:1) 833's; A-body and B/E-body. You will obviously need the short tailshaft A-body version. There is also the 833 O/D (4th gear is .73:1) which could be found in later A-bodies, F-bodies, and trucks. The A/F-body O/D's have short tailshafts, while the truck O/D has the B/E style tailshaft. These are said not to be as strong as the regular 833, but you have an overdrive in 4th gear. A 6 cyl 833 will transfer to a small block as long as a small block bellhousing is used, but you don't see too many 4 speeds behind 6 cyl's. When buying a bellhousing, make sure you get one with an IBR (input bearing retainer) hole that is the same size as what the IBR on the transmission is. The IBR could be 4.35, 4.8, or 5.125 in the case of the 833 O/D.

You also will need all the pedals, linkage, flywheel, clutch, pressure plate, clutch fork, shifter linkage, and maybe a different driveshaft depending on what transmission you have now.