centering rearend?

some decent books in general to check out are

Chassis Engineering - Herb Adams

and

The Multibody Systems Approach to Vehicle Dynamics - by Michael Blundell and Damian Harty.

not saying the talk about air ride at all, but they will give you a much better understanding of how to use geometry and math to understand what's happening.

Just a couple i've had to read for work.

personaly i do the criss cross method of measuring 2 square my rear end ill find a common point on the frame after i set my wheel base and measure from that 2 the opposite side of a common point on the rear end do the same for the other side once ur measurements are the same u know ur rear end is square and centered

I do the same thing, but that's also assuming that the points that you start with are square.

is isn't a real long back-halve, its in a s10 blazer 2dr. from about 8 inches in front of where the back seats were. even if it weren't square it would not make that much of a difference(allthough i know it is square, i have built framing items for many things at work). the lower four link bars are mounted to an area on the stock frame and the uppers on a crossmember. so besides holding the body the other purposes of the rear frame is to attach the shocks and hang the gas tank from. i know there is some holes in the frame i can measure from, i am just not sure how far back to put the axle at, how far should the driveshaft be slid out at ride height? i'm sure it should not be tight into the tranny, but probably should be pulled back slightly, even if only a half inch or less maybe? all i can do is eyeball it to the center of the wheel opening, or use a plumbob to see where it initally was. but the truck was hit on the pass. side rear at one time so i can't be sure that it is positivly sure that would be completely accurate either.

You are definately on the right track. You need to build your rear suspension first and then cycle it to see how much plunge the driveshaft ends up with at the trans, then have you driveshaft modified to keep as much yoke in trans as possible (to an extent.) As for centering the rearend in your fender well, I use a plumb bob too, but I figure out where the tire looks centered in the wheel well, not where it was stock. S-10s are notorious for having a shorter wheel base then the truck is long.