1965 Barracuda 273 rebuild...intake code?

The 1964 and 65 heads have intake bolt holes ~16 deg off vertical versus 45 deg of later heads. Your intake bolts appear to go in at 45 deg, making the bolt heads sit flush against the head. That suggests that someone drilled and tapped new holes in your 273 heads. Since you have the intake off, look closely. I think these holes would be in a slightly different spot, higher up, than the original holes. I installed a later aluminum intake manifold on my 1965 273 by making the tops of the holes conical (large drill bit in a hand drill) and flat-head allen bolts (tapered underside) to kind-of fit. I did have a slight steam hiss at the front cross-over, but tightening the bolts fixed it. Since then, I got the correct after-market 4 bbl intake manifold for my engine (angled holes), though haven't installed. Rare but parts eventually turn up on ebay if you keep checking.

I installed hydraulic lifters in my 273, so I could to use Rhoads leak-down lifters. I bought shorter ball & cup pushrods for a ~1972 340TA engine, which also had adjustable rockers (different PN's) w/ hydraulic lifters. Most likely, someone put later stamped-steel non-adjustable rockers on your 273 heads. If so, too bad you lost the adjustable rockers since people will pay >$100 for those.