My 1974 with a 2.3 only had an EGR valve, charcoal canister, and PCV valve as far as emissions went.
My 1976 with a 302 has an EGR valve, PCV valve, A.I.R. pump, a charcoal canister, and dual catalytic converters for emissions gear.
My dad's 1976 and 1977 Mercury Capri each had 2.8s with smog pumps, EGR, PCV, and charcoal canisters.
It seems the 2.3 cars got lighter emissions gear (even my 1988 Mustang didn't have a smog pump, and only had two small catalytic converters) but the 2.8s and 302s got "the works" from the factory.
Seeing as Mustang IIs range between 30 and 34 years old though, they've mostly been modified to some extent at this point, and I'm sure a large percentage of them aren't running the original exhaust system anymore (my 1976 with a 302 is a rare exception, all the original Ford crap still under it!)
__________________ 1976 Ford Mustang II Ghia: 302 with a 600cfm Edelbrock carb, Edelbrock Performer 289 intake, Dynomax Blackjack headers, 2.5" exhaust with Flowmaster Super 44s. RJS 11-gallon fuel cell, C4 tranny, chrome 16" pony wheels, fuzzy dice, brown vinyl half-top, and painted in the tackiest color ever (harvest gold, that's why I call it "The Goldenrod").
Also have a 2003 Dodge Ram (lightly modded daily driver/tow rig/office/dining room/home away from home/workshop... I call it "The Big Blue Dawg".) | 
Catalytic converters,which years,models? 
