With the BOSS (3600 lbs., 444 hp, 8.1 lb/hp) arguably called "the Best all-round Mustang ever" by magazine testers, it will take a Camaro of great(er) substance to equal/better its foe. 1SSs curb at 3850 lbs. and a few tricks may get that down by 50-100, after adding heavier upgraded suspension pieces. Which, to = BOSS, requires well over 460 hp. And the only non-boosted engine on the RPO shelf ready-to-go would be the LS7 (converted to wet-sump) which, @ 505 hp and a curb of 3750 (?) = 7.43...very close to the ZL1 but MUCH lighter (especially up-front) and therefore MUCH more nimble...
If the Mustang is BOSS, then meet the CAMARO C.E.O.!!