Kirk, way cool setup.
I'll write below about my stack injection, but first....
We raced 360 & 410 dirt, wing sprint cars for 14 years. Our sprint injection isn't much different than yours, since both are not electronic. Other than a little tunning on pretty cold or hot days, we'd change the fuel pill (which is basicly a needle/seat) We could turn down the idle to purr like a cat and still get great throttle responce. Talk to any sprint car engine builder or tunner and explain your situation.
I've always wanted two things in my Cobra, a side oiler (which I just bought a 428 for a great price) and stacked injection with the FAST system, but I may get a stand alone system.
The ori1ginal owner had it on a 445ci FE. He's taking his truck back to original, so out goes the injection.
Have you thought of buying a computer system ?
I know with our constantly changing weather here in Nebraska, I'd be tunning a mechanical injection,.....constantly, especially with the grains of water, or humidity/dew point, and the cold fuel.
Here's my TWM/BORLA.