727?

I'm assuming that they'd be the same size then and fit in an a-body without modification?

They should bolt in the same as a small block 727 would which means you would have to find a different driveshaft but everything else should swap over.
Like Grinder says though,why bother? unless you're installing a big turbo,a linelock,and slicks,or planning on pulling a 30' travel trailer with it,you're just adding weight to the drivetrain and to the car for no reason.