273, or 318?

If I went with the 318, I was planning on getting a block, preferably an early one. Do you think the bigger bore would counter act the smaller ports? I plan on cleaning them up a bit.

it is all original numbers matching. The heads were off and had guides put in. Still had 1966 bearings in it!
A "early" 318 is no different than a late 273 except for the pistons and rings. Unless you find a freshly overhauled one, you will need to go through it to make it good anyway.