Speed Density actually runs really good until you get into heads/cam or a SC. I've had around 10-12 5.0 foxbodys and the SD ones ALWAYS were quicker with the normal bolts on vs. the MAF. 87-88 are the fastest foxbodys other than the 93 Cobra and even then a stripped down 87-88 coupe would probably beat one of those stock for stock too.
My 88 LX coupe after I sold it ran a 13.74@103 with just gears, exhaust, and pulleys and would have easily ran low 13's with slicks. Then with a AFPR maybe even quicker..
Too many people jump onto the MAF swap WAY before they need to. A guy I know that had a 88 GT years ago did the MAF swap, chip, 75mm MAF and it was not any faster or better running than when it was SD.