Your post is quite helpful. I am new to this group. I have a 65 dart gt does the motor monuts work for this year as well? I am really trying to o the cheapest and easiest way to hp.
Power potential is pretty much determined by head flow. Stock 273/318 heads are good for about 300hp, 1.88 valved 340/360 heads are good for about 375 hp and 2.02 340 and magnum heads are good for 400 hp and EQ's and edlebrock 450 hp.
So the best bang for the dollar is to get a good running 5.9 magnum just 4 bbl and headers is said to make 320 hp and add a cam for another 30 - 80 hp depending on how aggressive your willing to go.
I'd go with the largest cam you can get away with stock stall probably around 215-220 duration.