Best steering box is from any 70's to early 80's chevrolet car (caprice,parisienne,Camaro etc...)
The Camaro has a fairly beefy dead straight pitman arm too.
The CJ 7 steering box is the same as the GM car box
They were all made by Saginaw gear, all the Saginaw pitman arms are the same spline and are basically interchangeable
All Saginaw steering boxes up to the late 70's used the sae45 deg inverted flare fittings... later ones use a GM only o-ring style fitting
the best thing to do is to find the steering box and pump/hoses off of the same car and remove them as a complete system (be wary of boxes that have sat open to the weather........
As far as mounting the box to your frame... I reccommend using the factory YJ box mount which should be installed with grade 8 rated bolts and sleeves through the frame (welded professionally prefferred)
the steering driveshaft can be sourced through places that sell Borgeson components (ie: NSOR)
As far as mounts for your engine (Chevy 2? four cylinder, iron duke 151? there should be stock brackets that will fit your block (maybe off of a Vega or from a straight six?)
You will definitley like power steering on the CJ2a, I know I do.........