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!
Since it's a all original number matching car, I would go with the 273 as originality is worth more money.