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?

What I did was just pull the carpet back and use blocks to position a flat square tube frame on the floor, and then measure from the corners of the frame to the floor for risers in different lengths at each corner.
Eye it, adjust, check for the same level on each side and adjust as needed as I went.
It took different length bolts at each corner as well, so it wasn't quite a whole day to get them in there with all the measuring, cutting and welding involved.

It wasn't quick or easy, but it was worth it.:D

Integrated belts would be nice, but I just used my existing lap belts.
I did put 4 point harnesses in as well just in case, but not having a cage there wasn't any good place to attach the shoulder belts.
This means a hard hit could cause the belts to crush the seatback and break ya.