I'm 6MT, stage 2 91 octane with basic supporting mods. Downpipe, Ebay Wagner clone IC, clutch kit, and so on.
Mustang is 6MT and stock powerwise. It has a catback, chassis mods and a nice short throw shifter. Also running 91.
Results are as expected. 5.0 pulls away easily with its top end grunt. I drove the Mustang plenty and it's a wonderful car. The power builds linearly and peaks basically at the limiter so you really have to wring it out hard.