350 to 700r4 swap
 

I have an 85 c10 with a 305 and a th350. I want to replace the 350 with a 700r4. The 700 should bolt up with no problems, but will the crossmember need to move? Also, will I be able to use the linkage from the 350, or will I need to find new linkage? Will the lockup swith from the 350 work with the 700 or does it need to be replaced too?

Yes the crossmember will have to move back about 2". If your TH350 has a 9" tailshaft your DS length will not have to change as they are about the same OL length. Yes you can use the linkage from the 350, but if you set it up normal you will not be able to select 1st gear. I put mine in first and set the linkage, it gets all the gears, but the pointer is a little out of line. I think to make it work correctly you need a column out of a 4spd truck.

This is how I'm wiring up my lockup circuit. All these parts cost me $65. It will be a little more if you dont have a friend at the parts counter.
http://73-87.com/7387garage/drivetrain/lockup.htm

Thanks for the info. The kit you linked to looks like it was designed for vehicles that did not come with a lockup converter. Mine has one with the 350, I was just wondering if it would work with the 700 as well, or if I needed a different switch or plug-in. Thanks again.

You can use your column, As stated by "bluex" you will have to select first gear on the tranny and then slide the bolt linkage to meet that spot, go to the dealer and purchase a plastic 4 speed tranny indicator and install it in your instrument panel where your three speed unit is. I have had one of these for years, works great.