The main difference i know of between 70 and later years is the interlock linkage. To connect the key release linkage to the shift linkage, the end of the linkage where it attaches to the transmission shift lever is different.

In 70 one piece of linkage had a long pin that went through the shift lever and through the other piece of linkage. They are held together with a clip through the pin.

In 71 the pin on the shift linkage was shorter because it didn't need to pass through the second piece of linkage. I believe in 71 they also switched to a push in retainer on the lever. If not 71 soon after they did.

If you are not using the 70 interlock linkage you don't need the 70 linkage but the shift lever may be different. Shift levers are not a big deal though.

You can see from the pictures the 70 with interlock and 71 up without interlock.