These are stardard size - replacement parts for all front drum brake models in 1967-69 Firebird & Camaro.

Supplied outright no exchange needed.. so no need or returning old units.

When replacing brake shoes in older cars..its worthing having the brake drum size checked by a proffessional brake service .. have them "cleaned up" but light machining.. and they will then be able to have each drum machined to exact size both sides..this will help in determining if you can still use Stardard Shoes OR if you need to use oversize..which are traditionally 1/64th or 1/32" inch over.. which THEN can be used to  radius grind both standard shoes and oversize shoes..to suit your brake drums.. so the radius on both are matching.. giving you a 100% chance of friction contact of the entire shoe.. as it was originally meant to be.  BUT this is more older school specialist brake repair service stuff.. not novice stuff.