Aftermarket bucket seats into a bench seat car- concerns and considerations?

Those seats look great! I have looked at OEM BMW seats as possible donors. Like yours, they usually seem to demand a recovering job...which I don't have the time or skills to do right. I've also looked at old Porsche seats and even Miata seats.

Fabricating the mounts seems a bit complicated.
Is there a thread or another resource on how people have done this? Is there a commonly accepted method?
If you find seats from a late model car with a convertible top they will have built in shoulder belts.