318LAs didn't come to A-bodies until 1967 and after that, 318heads were the same as 273 heads. So IMO , I wouldn't worry about what they mighta come on. The heads don't care about the valve gear or the lifters.
However the 64/65 273 heads are an orphan with the intake-bolt oddity, no biggie on a lo-performance build, nor on a higher if you already have a matching intake.
On a concours build well then the 315s are correct for 64/65, as the 273 was the only V8 engine available in an A-body.
66 was a kindof transition year.