4-speed to auto conversion questions

I've been thinking about converting my 70 340 Dart from a 4-speed to an automatic, I already have a small block 727, torque converter, aftermarket shifter, kick-down linkage and an automatic brake pedal assembly. Do the 4-speeds and autos use different driveshafts? Also, does the pilot bushing have to come out or can it be left in and is there anything else I would need to do or change? Thanks in advance.

I believe that shafts are different. The pilot bushing can stay as long as it is the factory style bushing. Aftermarket can fit into the register that the torque converter hub would fit into.

IIRC and it's been a few years, the A/F/M body A833 is shorter than the 727, whereas the B/C/truck A833 is the same length. So the drive shaft would be different.

A bodies used the same length Automatics as the B, C, E bodies but the 4 speeds were shorter so the driveshaft for the auto will be shorter than an original 4 speed in an A body.

Nearly all 4 speeds use the same yoke as the 727 but IIRC there were some A bodies that had the same yoke as the 904 transmission. If my memory is correct then I believe it was the later model feather lite & the overdrive A833's. You should check the yoke size before you have the driveshaft shortened or made.

Like somebody said the 1970 oem pilot bushing does not effect the torque convertor. Only the later model and aftermarket ones that sit in the torque convertor register hole.

I think that is backwards. The auto driveshaft for an A body with a 727 will be too short for an A body 833 swap.

However, if it's a 904 trans it will be the same length as the A body A833, or close enough to work.

I think we are saying the same thing but maybe my wording was a little vague?

A B/C/E 833 and 727 are the same installed length. Driveshafts will swap.
An A body 833 is shorter than a B/C/E - 833 or 727.
So the the driveshaft for the 727 auto will be shorter than an original 4 speed driveshaft in an A body.

I did not know the 904 was the same as the A body 833. Cool info.