you have one of each. AMT and MPC both did 1971 and 1972 Chevelle kits with the MPC being the promo. MPC has the dated rear bumper, interior with molded in rear seat and better interior details than the AMT. AMT has the 1970 turn signals on the lower front fenders and utilized one centered tab in the rear of the glass and interior tub. LMK if you have any other questions and I might have some extra parts if you are missing some.
Marc @ MPC Motorsports