Critique/suggestions on 273 engine build

A long time ago (1974) I poured money into my 273. Headers, high compression pistons, Offy manifold, Holley carb, street hemi profile cam, Isky Valve springs, windage tray, dual point distributor, etc. because that was the engine I had. It was a screamer for what it was, & I had a lot of fun with it, but a decent 340 or 360 would have walked away from it. If I were you, I'd start with a 318 at the least.

Since you have the engine already, I suggest the headers, something to bump compression (pistons would be better than head milling but they're probably next to impossible to find, maybe EGGE's has them?) & a mild cam, maybe one of those you mentioned. But be very careful with your cam selection. The 273 doesn't make a lot of torque, which is what you really want on a street engine unless you plan to add gears & wind it up. I ran 3.91 gears too. My engine saw at least 7,000 rpm once & never seemed to suffer from it.