66-69 273 heads are the same as the 318 heads with the standard LA intake holes ready to take any modern LA intake. I like the Stealth, very close to the sought after dual plane D4B and small port. trouble you'll have is low compression with a later 318 head as they were open chamber heads with exception of the very early 66 273 style or the '302' swirl port heads that may have that casting bump that may interfere with the stock manifolds. Isky E-4 is a popular 273 replacement solid cam with the E-3 being hotter. I used a Herbert Stage 2 cam (no longer listed) in a 318 when my 273-4 spun a bearing and I had to get to work monday. That motor was a great 318 in that 65.