I am finishing up my frame and installed the rear shocks today (Summit Adjustable). Without the body and engine on the frame how stiff should the rear be. Also, I put new rubber rear bushings in the top. Should these be left loose until the body and motor go back in or tight? Also, does anyone know what the measurement from the floor to the rear of the frame should be (in front of the rear bumper) Mine seems to be alot higher than when I took it apart. Thanks...

without the weight on the suspension, it will be pretty stiff. You will probably be able to move it, but not a lot.

Did you tighten the bushing bolts already? If so, you will want to loosen them until the car has the majority of the weight on the wheels. The bushings are pressed into the control arms and the inner steel sleeve is tightly held between the tabs on the frame, so when you set the car down to ride height, you will be twisting the rubber bushings and preloading them in one direction. Most likely, the rubber will shear inside the bushing. Then you will have to replace the bushings again.
All that is if you are using rubber, factory style bushings. If you are using poly bushings, they should allow the arms to rotate freely because they aren't glued to the shells or the sleeves like rubber ones.

Hope that helps

K