We installed a 1995 5.9 with the A518 in my wife's cuda with the stock computer and cruise control. It will boil the tires off and gets 29 mpg with 3:55 gears. There's absolutely no reason to screw around with the computer.
Everyone that I've talked to that started trying to reprogram the computer, never did get the car running as well as it should have. I say leave everything stock.
We had to alter the torsion bar crossmember, bend the floor in a little near the accelerator pedal, alter the trans crossmember and shorten the driveshaft. You can use a mallory efi pump and add a regulator with a return. We added a sump to the tank but you don't absolutely have to.
Most reliable musclecar out of the twelve cars that we own and drive.