I'll preface this by saying I'm far from being an expert on transmissions, but for what it's worth:
has the best info on bellhousing bolt patterns and years, but they DO have mistakes in some of their info. I found their online catalog
(which has to be dl'd into Acrobat) and here are some excerpts:
"Ford V8: Ford V8s use three different block bolt patterns. These engine groups can be found on the bottom of Page 43. Most of the adapters and motor mounts we offer are for the Ford small block. Ford used two flywheels, 157 tooth & 164 tooth. These starters index and bolt on to the bellhousing. It is imperative that you match the flywheel, starter and bellhousing. If you mismatch any of these items, it will only cause you grief! The 351 Windsor is considered a small block but has a few differences. One difference is that the heads of the block are wider. This may cause exhaust clearance problems on some conversions. Another difference is the oil pan bolt pattern. Conversions, such as the Bronco II, require a special oil pan that may need to be purchased."
"SMALL BLOCK FORDS: 289, 302 and 351 Windsor all have the same block bolt pattern.
FORD BLOCKS: 332, 352, 360, 390, 406, 427 and 428 all have the same block bolt pattern.
FORD BLOCKS: 429, 460, 351 Midland and 400 Midland all have the same block bolt pattern."
The only differences between a 2WD & a 4WD AOD (assuming they're both going to be rebuilt & beefed anyway) are:
(of course) the tailshaft & its housing which can be unbolted & swapped;
the filter & its pan - the 4WD has a ~2" square x ~1" deep sump in the middle of the pan & the filter has a pickup tube that matches;
the breather on the top of the case - 2WDs have a stub with a cap but 4WDs have a short rubber L going to a long metal tube that runs up the spine to a bellhousing bolt & then down the L side beside the kickdown cable bracket.
(I'm pretty sure all AOD's are RWD - I think the FWD tranny is AXOD.)
When I had the AOD rebuilt for that '75 I did, they guy who rebuilt it recommened (& I deferred to his experience) putting in some Mustang components in the tailshaft/pump area for strength, durability, & performance, but I don't remember exactly what parts he substituted.