Heads, Intake & Carb upgrade...

I grew up in the mountains of Colorado (just west of Denver). I also had a 318 in my Barracuda at one time with 3.23 gears. With a mild cam it ran 16.5 at Bandimere. With a little more cam and a swap to 360 heads I got it into the high 15's.

To answer 1 of your questions, the 650dp is just fine, that is what I ran on my 318. Switching to a 360 would help a lot, especially if you can get it to zero deck and get some compression. The last engine I ran in my car before I left Colorado was a 360 with OOTB Edelbrock heads, Mopar performance "509" cam (don't do that, that cam sucks), 4.10 gears, 727, 3500 stall and my little blue friend....NA the car ran 13.5-13.9, on the bottle it ran 11.1 @ 122mph. If you are at altitude and have no atmosphere, just bring your own...in a little blue bottle :-)