I deally you want to find a HP D44 from anything before 1978 Ford pickup. The 1978 & '79s have the radius arm mounts cast as one piece on the pass side & you cannot modify it. The 1976 & 77 will have disc brakes, before then will be drum & you would have to swap them on.
FWIW, the R&P strength of the HP D30 is comperable to the LP D44. If you can't obtain a HPD44, you will have to weigh the costs/benefits of losing ground clearance w/ a LP D44, the cost of the swap including coil mounts, different pattern wheels & stuff
VS.
Paying to upgrade HP D30 axles, hub conversion kit, strenghening the housing, Etc.
Either way it is not cheap
If you are not a purist, I have seen Toy axles under Jeeps - they work well and can be an economical alternative:anon: