Slant six to five or six speed trans.

I have been trying for several years to find a bellhousing, an adapter or some method of replacing my 4 speed with a modern 5or6 speed transmission. I have come across lots of “do this” or “do that” ideas on the internet, most would seem to be backyard sketchy **** conversions. If someone knows of a method of putting a new transmission onto a slant six that is done properly, I would love to hear about it. I have talked to all the companies who make 5or6 speed gearbox’s, but no one, as of October 2024 offers a bellhousing or adapter. I did find one place which said a bellhousing from a mid 80s truck slant six can be adapted using a custom made adapter plate between the bellhousing and transmission, but I could not find any details about that. So any help would be greatly appreciated.