The factory ecm is underhood, but I wouldnt ignore anoher option if it was a under dash unit. It wouldnt be much more work just to run some extra wire and mount it inside. Whats the datalog speed on that ecm? If my plan for tuning my factory one bombs, then I would want at least the same datalog speed at the 7427 I have in my cherokee, or faster.
Also, It would be nice if I could reuse as many of my factory sensors as I could. I already have a 1x cam sensor, and it look a lot like the gm ones I have seen pictured on here. Its also a speed denisity (MAP) based system. I think DIS would be a added plus, if possiable. I dont really want to swap to a older modded non FI distributor, I would want a crank triggered system. I know my factory crank trigger would not work, as the notches in the flywheel wont match up to anything gm uses. But my harmonic blalancer has a nice lip around it that would lend itself to being machined real easy.