273 time to 'fish or cut bait'...
What I want to do is build an affordable driver that uses pump gas and will wear out the tires every few hundred miles. Something to drive cross country on state highways. I'm thinking 0-60 time (to get away from F***ing stop signs and lights, running 60-80 for most the day without getting tired, and milage as good as my pick-up truck (F150) would be most important. Passing Chevys would be a big plus also...
Your in over your head, with a 273. She cannot hit more than two, or maybe three, of these bases.
You really need a slightly warmed up 360, to cover them all.
The 360 with a 2400TC will pull 2.76s for mileage, comfort and reliability. It will take off really well. It will annihilate those other brands. And with a 220 or less cam, and pumped up compression, and a good tune,will surprise you with it's frugality. It costs the same to build or nearly so, and you can paint it to match the 273. Problem solved.
Yeah, I know what your thinking, but you posted too late, now you are almost married to 273 power. So you are gonna have to rethink some of your "wants". Or take your licks on selling the 273 stuff.
But I gotta tell you; I once put a 340 in a 65 longroof with a 904. It did everything on your "want" list and more. The 340 had a complete teener top-end on it including the cam. It was basically a big-bore teener.
360s are cheaper easier and better.
Of course there are some things that the 273 can do. They just can't do all the things you want it to, unless you supercharge it. but that kindof throws 2 or 3 of your targets right out the window.