1965 273 2 bbl engine.

As stated, the intake bolt size and angle, the pistons and the water pump are the only things that make it different than a 318. I used pre-magnum heads on my 273 (swirlport 318 heads) and a LB4D intake. I had a performer that I could have used, but the thermostat angle wouldn't work with my AC setup. The 273 is a great underrated engine. The only part I had issues affording was the 10 to 1 pistons. Luckly I was able to reuse my stock slugs after sleeving a couple cylinders.