Most everybody whose done a swap into an older car has run an aftermarket injection system. Check out
www.wmsracing.com their system uses the original harness and sells for $1000 USD. It may sound like a bunch but it will be much easier than chasing demons with a stock computer plus you can sell off your MAF to recover some of the cost. There's a guy in Calgary running a nitroused 5.4 L notch with the DOHC navigator motor with the WMS dfi system and it runs like a factory car.