A 78DA-7003-AB gearbox, is from an 81' onwards XD They were used in either 3.3/4.1 or 4.9 XD's, possibly very early XE's. Shorter ratio gearbox, I believe

Looking at the Exedy website, all the single rails (even 3speed) are 10 spline on the clutch friction plate 3speeds just have a smaller diameter shaft at 24mm, over 27.5mm   The info regarding 19/20/21/22 splines, relates to the opposite end of the input shaft, internal to the gearbox?   First screenshot is all XD, and XE up to 05/82 Second screenshot is XE only, from 05/82            

Would you mind trying to decipher my tag.  Judging by all the research I'm doing I'm hopeful the first gear ratio isn't to high as I have plans for it getting bolted behind a 351c Seen Chestnut comments saying he had a 015 but 016 could be different all again 

i had a quick look through that,   I've never known one to be different, but anything's possible with Ford i guess. 

odd,  i've never seen a different clutch plate needed unless it was for the 3 speed or the rubbish 3.3gearboxes (mitsubishi sigma box in 4 or 5 speed i believe )

i'd just count the one on yours

Was off the very detailed post Sparky had put up a number of years ago 

I'd disagree with that screenshot info

wonder if @Thom or @SPArKy_Dave could help confirm it,   they are all same as whatever a T5 is (pretty sure it's 10 spline) 

That screenshot has the info that I was going off.  Been talking to the bloke on bought the package off, feeling confident gonna be OK & have now done a deal for the Flywheel, pressure plate etc that the previous owner offered him 

XB to XF sedan tailshafts would be the same for bw35,bw40 (auto) C4/C10, single rail and T5 manual.. you'd be able to use yours.  FMX and top loader have different spline count on the tailshaft yoke..      clutch splines are the same from my understanding single rail to T5 (not sure on the V8 one but betting it's same)  the 3 speed had different splines into the clutch (input) and the top loader one might be different?(no idea)  6cyl didn't have 20 spline input, well unless the sigma style 3.3 litre box had that much on it, it's super rare by comparison and is bolted to the bell housing from the inside .. and would barely handle a 250 crossflow let alone a V8..