The 5.0 was 4 tenths slower than the iroc? Was the mustang driver making a sandwich between shifts? My 89 lx 5.0 5 speed would always beat the local duder’s 350 iroc maro. Didn’t the 86 5.0 have the awful peanut heads?
87/88 notches were the fastest, as they didn't have the 55mm mass air meter in their way. They were 300 lbs lighter than a 5.7 IROC, had about the same power and no real losses through the 5 speed.
86 had the one year E6 heads, small runners, shrouded valves, and true flat top pistons with no valve reliefs.