Which engine?

The thing about a 360 is low-rpm torque.
If you like to put it in drive and just drive, it's hard to beat a 360 in a lightweight-A like yours. You can leave 2.76s in the back and up the TC a tad and leave the engine stock, including the big 2bbl.
I once did that with a 340. I put all the 318 top-end on it including the cam. It was dynomite. First gear was good to 60mph-plus and it boiled at least one tire most of the way there.
If you start with a Magnum, you will be ahead of the game.

There is only limited fun to be had with a 4-gear and hiway gears.
The Magnum can be set-up to rev 6000 easy and cheap enough, which will get you 60 mph,with 2.76s, so no shifting there :(
Around town shifting easy, I like 2800. This will get you about 28mph in first, and 39 in second, and 53 in third, and 74 in fourth.
Cruising is about 65=2460 with those 2.76s and 24.5" tall tires. So there you have your boring shifts. But hiway cruising is sipping gas.

If you go automatic;
The 360 will pull this gear pretty sweetly. If you need a little more off the line, I suggest a 2400 to 2800TC. I would go straight to the 2800, but that's just me. With the 2800, out here on the prairies,you wouldn't have to downshift to pass at 60mph.
There is no reason to not drop the running 273 in for now. But I,that's me,I wouldn't spend a nickle on a 273. Bin there done that.Well, I might turbo it.....:). Naw, just kidding