Other than the bellhousing (I believe the AU 1 can be bolted onto a EL trans) will an EF EL trans fit/work in a AU falcon?

i guess your refering to auto??
yes, ea2 btr to the au btr can all be interchanged, there are some minor differences but nothing that will cause issues..except ef onwards have a different pump which takes a slightly different torque converter..

ive got a eb auto bolted up to an au belhousing..