If your center bearing (supporting the center u-joint at the front half of the driveshaft) is going to be fixed to the frame (as it should be), then you really only need a slip joint on the rear section of the driveshaft. That's where the shortening of the driveline is going to occur with compression of the suspension. But if the tranny you're planning on using has a slip connection, it won't hurt to include that on the front section.
Thanks. By rough guesstimate, lets say the sm420 is a little over 10", add a bell housing and that adds 6"-8". I would expect to lose 11" - 13" inches of front driveshaft (Short housing TH400 is approximately 29"). Now new question, How much HP can the center support bearing withstand? As my 383 is near 500hp. The stock center support bearing had the 235 (little over 120hp) and SM420 in for a few years and is showing signs of cracking. What are you using for center support (on a SBC with a little HP)?
