I'm gathering parts to eventually convert my 1970 F100 360 3-speed to C6 automatic. I know the manual and auto crossmembers are different, does anyone know for sure if a dentside crossmember is the same as a bumpside? Found a 78 and 79 in local junkyard, both auto, and want to get a crossmember if it's the same.

 

My 68 was originally a 360, 3spd. When I put in the 351W + C4 I used the original trans cross member. It can move back and forth considerably and you just drill new holes in the frame for where it sits. I just pulled my C4 and installed an M5OD R2. I used the same cross member but had to slide it rearward about 5" and drill new holes in the frame. Just be aware to check your pinion angles.

 

Bumpside F100/250 and Dentside F100/250 crossmembers are different part numbers
C8TZ6A023A....68/72 F100/250 4X2....360/390 A/T.
D3TZ6A023A....73/76..F100/250 4X2...360/390 A/T.

 

The most relevant info, Jeff, is that the frame widths are different between bumps and dents, except for 4wd F-250's to 77. That is also why dent crossmembers won't fit in bumps.

 

They are different from the cab back. Where the transmission crossmember bolts in is the same. People swap dent I-beams into bumps all the time to get disc brakes.

 

I'd take all the measurements on paper of yours pictured of all the specs important shapes etc. have it in hand when your at the junk yard to match it up to a vehicle you think will fit.

That way you'll have a better idea what's what!

In stead of hear say, then all screw ups will be yours.

Orich

 

I converted my '69 from C6 to 4spd toploader. Just slid the crossmember and redrilled the holes. They are simple.

I know the 80-90's trucks have different crossmembers as I converted my '89 and it took a different crossmember. The crossmembers are much more involved on newer trucks.