Convince me to put a TKX in my Dart

Very good points, @DionR . Currently I do mostly city driving and limited highway miles, like you mentioned. However I do want to road trip the car and that was one of the big motivations to do this. Everyone has to seriously consider the rest of their setup to find the best fit for them.

I'll shed some light into personal my setup, and my train of thought for the TKX.
Stock stroke 360, 11:1 compression, 250/258 @ .050 Isky solid, heavily ported heads by Brian at IMM, ported Victor 340 intake, 850cfm race Brawler, 1 7/8 TTI headers, 4.10 gears and 28" drag radials. It's a small 360 that makes more power than a lot of 408's (just over 500hp). But as you can imagine, it's not happy down low. Its happy idle is ~1100.
So for me, the sweet cruise spot I was looking for was 75mph at 2500rpm, which is exactly where the TKX places me. The engine is super happy there, has just enough torque that I wouldn't be lugging it up a slight hill, and gets okay gas mileage. A T-56 would almost put me down in the choppy region of the cam, which would make absolutely no sense to me, while also costing about a grand more! Considering I was used to cruising the highway at 4000+ rpm with the 727, the thought of 2500rpm sounds like heaven.