OK, now the waters are getting muddied a bit. That's not the original trans. Looks to be an SM465 (you can tell from the PTO port on the divers side), which replaced the SM420 in '67. In some ways, it's a better trans in that it is full syncro, rather than syncro in 2-3-4 like the 420. However, it doesn't have as deep of a first gear ratio. It will have the later large diameter bearing retainer, which will make a difference on the bellhousing. You will need a bellhousing with the large index bore.
Most likely, it came out of a 2wd truck, as the 465 was never used with a divorced style T-case.
