My '65 Galaxie FE manual transmission bellhousing is a C5AA-6394-A. Some of these are dual pattern drilled for both the early narrow transmission-to-bellhousing bolt pattern and the later wide pattern. Mine is drilled for only the later wide pattern, complete with thick bosses where the wide pattern holes are drilled and tapped. There is plenty of meat for the transmission bolts to grab onto. The narrow pattern holes in 6394-A bellhousings that have been drilled for both patterns do not have the extra material bosses in the narrow pattern holes while the wide pattern holes nearby do. The difference in the bosses for wide vs narrow pattern can be seen here:https://davids4speeds.com/product/1965-67-ford-galaxie-toploader-cast-iron-bellhousing-390-427-428-fe-c5aa-6394/
So in theory, the narrow pattern trans can be bolted to the narrow pattern holes, but I'm puzzled about how strong the connection is since there's actually not many threads in the bellhousing for the bolts.
I need to bolt a narrow pattern T-85C-OD transmission to my bellhousing with the wide pattern-only holes. Of course I can locate, drill and tap threads in the bellhousing so I can bolt up my T-85C, but is the bellhousing really strong enough without actual bosses?
Alternatively, I could change out the T-85C case with a T-85N case that has the wide pattern to allow bolting to the existing threaded bosses. I do have the N case, so it can be done, but drilling and tapping for the C case would be a bit easier and faster.
Anybody have experience bolting a narrow pattern tranny up to the dual drilled 6394-A bells? Would there be enough strength even if bosses aren't there? Thanks for your assistance!