I have a 67 factory 3sp on the column with a 352 engine. I purchased a rebuilt c6 trans, automatic steering column with all the linkage, auto crossmember and the drive shaft from a buddy for $200. I also have a flywheel from a 360 that had an automatic trans hooked to it.

My question is will I have any problems with the trans tunnel being to small for the automatic or are all the floors the same?

 

You should have no problem.

 

Cross members are the same you will need a automatic trans. mount or you can use the manual one and have to drill new holes for the crossmember also you will need trans lines and a trans cooler.

 

TNT, The front cross member has to be pulled, or the engine to put a C6 into the truck. The 3spd cross member is riveted in not bolted like the ones from the factory with auto. Once in there are no problems. I recommend that you cut & pop the rivets replacing them with bolts, so access to the area can be had.

I stuffed my FE/C6 in and shortly afterwards had to pull the tranny for service. The rivets had to be cut or I had to pull t he engine.

The rear member will have to be moved rearward about 2in as well.



John

 

Thanks for all the info and advise.

 

I also did this to my 69 F100 (3sp to C6) the first year I had my truck, 1982 IIRC.
Like has been stated, the crossmember needs to be taken out and replaced using bolts. This for me was the hardest part, because at that time there was no such thing as a 4 in grinder(at least that I knew of), and I didn't feel comfortable using a 9" laying on my back under the truck. Also didn't have access to a set of torches to blow the heads off, so I ended up using an air chisel. I think I couldn't hear for a week, and it took a long time. I also found out that the rivets are installed hot, so they are not necessarily straight in line with the holes in the frame / crossmember. I remember getting the head off and thinking I could just punch the rivet through and out - NOT.
My rear crossmember was the same, but the auto trans mount made the transmission sit a fuzz higher. It was touching the hump in the floorboard - very slightly. It made all the noises of the transmission operating amplified so I could hear them - wow what an ugly sound. I thought I had bought a pile of bolts for a tranny.Sounded like shaking a can of bolts inside the truck.
I lowered the trans using the stock 3 speed mount, and the noise went away. Same trans is still in the truck and running perfetcly - 29 years later and a whole lot of miles. Those C6's are tough.
The work was well worth it, so much nicer driving an auto (had manual steering). Changed to power brakes at the same time, manual brakes came as part of the 3 speed package.
Do it, you'll be happy.