5.7L hemi Duster/resto.

Starting to mess with my rear triangulated four link.... Dose anyone have any good info on angles? lenths? ect. I have done some measuring and i plan to build my own. I got the tubing already. just looking for some input. I did some eyball mach. up and it looks like the top bars are goin to the frame rails, and will be aprox 12" long....is this to short? my lowers will be longer closer to 36" will the big difference be a issue with keeping the pinion angle corect durring normal travel?

thanks