I have 86 k5 with a tranny prob. Has a 700r4 in it. It goes into gear fine but when it shifts from 2nd to 3rd it acts like it kicks into passing gear. If you mess with it for a while it will go ahead and kick into 3rd but wont kick into 4th. I changed the fluid and filter, and govenor has suposivley been changed right before i bought it. If the tranny is bad does anyone think I can put a th350 4x4 out of a sub. in my blazer. I have heard you can, just might have to change the transfer case. If I can get any help on this it would be extremely greatful. Thanks.

The best part about GM parts is the swappability. You can swap in a TH350 or TH400. Things to consider. Make sure you get a tranny with the correct output shaft to fit your t-case. If you go to the longer TH400, you will have to change your front and rear axles. The front will have to be lengthened and the rear will have to be shortened.

Check out this site for K5 specific info.
Look around I believe they have all the details you need.
http://coloradok5.com/