how "tough" are these transmissions? like..comparable to the fairly bullet proof sm465.

also. whats the deal with the 4wd ones? could they use the same front axle and everything as in my '69?

anyone out there all knowing?

thanks, sam.

1967 Chevy II, 2-door post.
250, 3-OTT.

1969 GMC 1/2-ton.
307, 3-OTT.
DD.