[LMH]

Of those, the Jaguar is the closet to the original 4HU differential. There are companies selling brackets that allow the Jag unit to be used with original mounts like would be in an original chassis.
The ultimate would be an aluminum 4HU, available from a couple different manufacturers.
Kirkham makes and sells one, that's what I have. I think they're around $5000 or were a few years ago. It has the correct mounting bosses in the nose of the case. Gerry Hawkridge in England also has them. You can contact him at Hawkcars.co.uk.

Larry