I've been thinking for some time about doing this myself, but it's low on my list of priorities. Shouldn't be too hard, you just need something like a Uni-Ball Weld Cup of the appropriate size and then a section of DOM turned to the correct size to take up the space between the Uni-Ball Weld Cup and the control arm. I've done a lot of research and the trick is finding the appropriate size Uni-Ball weld cup so the ID of the DOM tube matches the OD of the Uni-Ball weld cup. Then only the OD of the DOM tube needs to be turned down to the ID of the control arm bushing hole. Then just weld the three pieces together. I think it could be done for about $80 in parts and about two hours labor, with judicious part selection to minimize machining.

Oh, and I don't think that sphericals make much sense on a Mk1, would be a lot more beneficial on the Mk2 Pt H bushing.