4 speed identification

Does the gearbox retainer fit the bellhousing hole? Do some research and make sure it's a pass car and not a pickup bell (You want the small flywheel)

Determine if it's an overdrive or "straight through" gearbox. To do that put the gearbox in 3rd gear. Do so by moving the 3/ 4 slider to the rear as per the arrow. Rotate the input exactly one turn while watching the tail shaft. If the tail turns LESS than 1 turn, it's a "straight through" 4 speed. If it turns somewhat MORE than one turn, it's an OD box

And yes that's a "slip yoke" gearbox. If it were not, it would have a bolt on drive flange at the rear

I cannot tell if that's a V8, SB, BB, or slant bell, but it looks like a SB. I don't know if the later bells will fit the older bodies

The broken teeth are 2nd gear

the "actual gears" visible in your photo are left to right on the mainshaft....3rd, 2nd, the straight cut gear is reverse, and the large helical one at the far right is 1st

If you don't have a shop manual, wander over to MyMopar and download "a couple." some of them came from the guys here on FABO

http://www.mymopar.com/index.php?pid=31