1966 273 Commando - Thoughts

If yur contemplating hiway miles to cruize-ins with a 273, a stall to match a 287/cam, and say at least 3.91s, then yur gonna need an overdrive. That's like 3000>4000, plus cutting up the floor.
For less money and better IMO performance, you can drop in any lazy-azz 360 with a 4-barrel and just leave whatever is already in there, in there. The downside is you loose the idle-lope of big-cam.
But the good news is, there are cams available specifically to cover that characteristic.
Plus, for a few bucks more, that 360 can be sporting a 10.7 Scr, and smoking 2.94 gears to at least 60 mph, which I know you'll never want to do, right? lol. Until the first time, lol, then you'll do it again and again and .............
Just paint it red and put a 318 top end on it, and it will still smoke the tires in your 67.