3 to 4 Speed Conversion

Piece of cake and your teener is gonna love the short splits.
If you get an opportunity to obtain an early-A box with the 3.09 low gear, your teener is gonna love that even more. However the early-A comes with a Ball and Trunion drive flange that has to be converted at additional expense,namely a different mainshaft and extension.
EDIT; between the A230 and the A833,from 67 up,I'm pretty sure the driveshaft length is the same.
Not sure about the slip-yokes.
My early-A, with the large diameter mainshaft installed, seems to be every bit as strong as the 2.66low box.
I haven't been able to blow it up...yet.