Has anyone ever built a 318/340/360 to look like a 273??

You are mixing things up a bit. 64 and 65 273 heads have intake bolts that are small, 5 16 using a 1/2 in socket, and at a different angle. 66 up are the same as all LA small blocks. All 273 and 318 ports have the same port opening, except for a few Pursuit 318s made in the 80s?.