right... I see you have 1 post only, so you are likely not a long term resident reader of these boards, so to clarify, the American 280Z is NOT the australian 280Z... what you may find in AU as a 280Z, is what the yanks call a 280ZX and nothing else. NZ, Aust and Japan markets went straight from the 260Z to the 280ZX without receiving the US market 260Z re-engined with the L28 and renamed the 280Z. As such, you are better refering to the aussie 280Z's as S130's or you may find americans advising you on the basis of S30 model 280Z's which are 260Z's with a larger engine, rather than the later all-new chassis S130 280Z/ZX models
Hope this clears up some confusion before it all starts.
As to the specifics of your questions, I believe the 280ZX's with autos had R180's and the manuals had R200's, definitive answers can be found in the comprehensive Diffs sticky in the Drivelines subforum.
The F54 is a siamesed cylinder block that some like, but the non siamesed actually in some cases had thicker walls and handled boost/boring better... either block will work fine, get them crack tested or magnafluxed and use the one in better condition regardless of the block casting.
All S30/S130 N/A 5 speeds were FS5W71B boxes, until the turbo 280ZXT which used a BW T5 box.