Changing intakes

I went the other way and countersunk the bolt holes of a 1966+ alum intake to fit to a 1965 273. I used conical flat-head allen bolts to kind-of fit the holes. I looked for such "hill-side washers" (post 8), but couldn't find anything that size or affordable, though I didn't know that name when searching McMaster-Carr. I wasn't happy with the ability to tighten the bolts and one water cross-over hissed slightly until I tightened more. I didn't worry about buggering a later intake since they are common. Since then, I bought a correct 4-bbl 64-65 intake so will probably swap. I sure wouldn't bugger one of those since valuable, especially your dual 4-bbl (extra rare). It is mainly good for bling and unlikely to give any performance improvement, and probably headaches.