904 or 727 ????

a 727 will fit a 68 Valiant without a hammer touching the trans tunnel....maybe the early A bodies needed it...but after 67 went the A bodies got bigger....nope..

in fact...all the 340 A body cars starting in 68 ...came with 727 from the factory......

That's kind of what I was going to say.
727's have been put in pretty much all the cars before by the factory.
Especially factory big block cars.