Well, of course the retainer must fit, the location of the new threaded hole in the case must encounter enough meat to share the load with the other three mounting bolts, splines count can be dealt with by disc. Obviously trans should be disassembled to allow the tap to cut threads all the way through, and allow the chips to be removed.

Ed

'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.