Slant 6 swap 170 to 225

65-71 auto trans changes that effect a swap.
1) Shifter change, 65 is cable, 71 is mechanical. Would need a 1966 steering coluum, or 66 up floor shifter. or aftermarket floor shifter.
2) Drive shaft. 65 had a B&T bolt on flange at the trans. 71 uses a slip spline.
3) Speedo cable. need a 1966 cable (will fit the 71 trans and the 65 speedo.
4) Change wiring on neutral safety switch

That is using a 68 or newer trans (auto) with a 68 or newer slant six.

If trying to use a 68 or newer auto trans, with a 67 or older slant six, you would need a custom built torque converter, as the pilot hole in the end of the crank got larger in 1968, and the 68 up converter will not fit the 67 down crank. You cannot use the 67 down converter in the 68 up trans as the splines changed between the two years.

You can use the 67 down trans with a 68 up engine just by using an inexpensive adapter bushing in the end of the 68 crank.

You must use the flexplate for the year engine, not the year trans.

Think I covered everything