1965 Offenhauser 273!

I agree. It's one of the best looking air cleaners ever. Probably too small for a high horsepower motor, but more than enough for a less than 300 cube motor. Shoot, Chrysler put them on some four barrel big blocks in the early sixties - 361s all the way up to 413s (only they were painted black, not chromed) .
nothing stopping you from cutting a big ol' honking hole in the back to free up some HP. nobody'll ever see it back there.