Use one of the Ford 8.8" aluminum IRS center sections out of an Explorer or a T-Bird, an 03/04 SVT Cobra or a MK VIII. Have your local fab shop build the bracketry to mount it. The one on the left is the Explorer and the one on the right is the T-Bird / SVT Cobra / MK VII unit. The Explorer is beefier in the front mount area.
Ford no longer makes the nice FRPP HD cover for their 8.8" IRS that looks like this;
Although they can be found used, you can also have a nice billet piece like this made;
The 8.8 IRS is extremely strong, light, small and fits in our chassis nicely. They have gear sets from 2.73 up to 5.71 available in both the aftermarket and OEM channels. The rear end has been used by various replica manufacturers over the years and provides very good service life. Parts are readily available and reasonably priced in large part because of the widespread adoption.
Almost forgot, here is a pic of the OEM Explorer rear cover. It is also quite robust.