additionally, of course, grab the driveshaft (if it's from a 140), as well as the matching flange off the rear end. Good chance your 4 speed car has the small driveshaft, and your donor transmission, driveshaft, and rear flange are of the larger type.

In fact, it would be helpful to know exactly what your transmission with O/D came from.. 140 tunnels changed sizes in '70 I think. Most M41s in 140s with the long shifter came from '71 142e cars. If your donor transmission came from a pre-70, or from a 122 or 1800, you will have to source some other bits along the way. Not a biggie, just need to have all the right parts before you start the swap, so as minimize down time.

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-Matt I ♥ my ♂