I remember when my brother bought a brand new 1988 5.0 Mustang LX. It was faster than the the GT and the Z28. At the time, I owned a 1986 Shelby GLHS. The ass-whoopin' the Shelby gave the mid 80s Vettes and pony cars was epic. 0-60 in 6 seconds. 1/4 mile in the low 14s. .94g lateral acceleration, and braking distances 30 feet shorter than Mustang, with zero fade (the Mustang's brakes would fade badly). Several years later, we pulled the 175 hp 2.3 liter and swapped in a 220 hp 2.5 liter. A close ratio gear box kept the power in the meat of the curve. Konis were standard. 205/50-15 Gatorbacks too. There's not many left of the original 500 built, but you can still find some doing SCCA SOLO events.
While it was simply one of the fastest, quickest and best handling cars sold in this country at the time, it was a complete disaster in terms of reliability. Head gaskets.... I think I replaced 3 of them. Fuel pumps would have the pick-up fall off (safety wired hardware to cure). Turbo seals were poor... I replaced the turbo twice. It also suffered from an intermittent dead short in the main wiring harness. Eventually, I replaced the entire harness (special order, not inexpensive). The upgrade to the 2.5 liter cured the head gasket woes, and pushed down the 0-60 times into the middle 5 second range. Pretty peppy for 1990....
However, when it was running,
God help the Corvette, Camaro or Mustang driver who thought his factory stock car was fast..... More recently, I owned a WRX. The GLHS was quicker, and better handling (much less understeer). OTOH, the WRX was reliable and vastly more drivable on a daily basis. You'd have to buy an Mitsu Evo or and STI to go faster than the GLHS, and only marginally so.... The GLHS was the Viper ACR of its day.
Edit: I found this website by a current owner of a GLHS... Minor re-tuning resulted in a 12 second 1/4 mile.... Not bad for a four door, four banger that's based on the old Omni....
