model year production years for gms started sept 01 .. so for 87s that would be sept 1 1986 . the 87 regal model year ran to aug 31 1987 but because of popularity and all the standing orders for gNs they made history by extending the production of GNs until dec 11 1987 . by all rights the sept 01 1987 through dec 11 1987 cars should have been labeled as 1988 models (the montes and olds produced then were labeled as 1988 models ) but that would have been a hard to let them out as 88s since they had announced 1987 as the last year of the gn with the gnx to go out on a bang
as far as the bumpers all Ts got aluminum supports it wasnt an option or special ,,the GN got steel supports and many have been swapped out for the lighter aluminum over the years
posi was an option except on the GNs built during the extended model year when the posi became standard with the GN (and they increased the price accordingly for the WE2 pkg)
non posi would receive alum drums , posi got steel drums except on the Gnx
many changed out the alum for steel when they needed replacement and many changed out the steel for alums for weight savings .
kirbansperformance will have brand new aluminum drums available soon