GM 15" x 6" Inch Wheel Cross Reference (FWD)
 
ET = Offset Go to: Vehicle Bolt Pattern Reference
H = High Positive Offset - FWD ( Front Wheel Drive ) Typically +45, 40, 35 offset
M = Medium Offset - RWD ( Rear Wheel Drive) Typically +20 offset
L = Low Offset - RWD ( Rear Wheel Drive ) Typically 0 offset
 
CB is "Center Bore" or the diameter of the hole in the center of the wheel.
 
MODEL YEAR OE SIZE  BOLT LUG NUT  CB ET
    Wheel Diameter and Width How Many Lugs & How Far Apart  Lug Thread Size & Pitch
Center Hole Size
Offset
Oldsmobile
CUTLASS SUPREME (FWD) 88-97 15 X 6 5X115 12mmX1.5 70.3 H
88,98 DELTA,REGENCY,ROYALE (FWD) 86-96 15 X 6 5X115 12mmX1.5 70.3 H
LSS 97-on 15 X 6 5X115 12mmX1.5 70.3 H
TORONADO TROFEO 86-92 15 X 6 5X115 12mmX1.5 70.3 H
SILHOUETTE 90-on 15 X 6 5X115 12mmX1.5 70.3 H
INTRIGUE 97-on 15 X 6 5X115 12mmX1.5 70.3 H
REGENCY 97-on 15 X 6 5X115 12mmX1.5 70.3 H
 
Cadilac
ALLANTE 87-93 15 X 6 5X115 12mmX1.5 70.3 H
DEVILLE 85-on 15 X 6 5X115 12mmX1.5 70.3 H
SEDAN DEVILLE 93-on 15 X 6 5X115 12mmX1.5 70.3 H
 
Chevrolet
VENTURE ?? OFFSET? 97- 15 X 6 5X115 12mmX1.5 70.3 -
VENTURE 97-on 15 X 6  5x115 12mmX1.5 70.3 H
IMPALA 99- on 15 X 6 5X115 12mmX1.5 70.3 H
LUMINA 90-on 15 X 6 5X115 12mmX1.5 70.3 H
 
Pontiac  
AZTEC 01-ON 15 X 6 5X115 12mmX1.5 70.3 H
GRAND PRIX 88-on 15 X 6 5X115 12mmX1.5 70.3 H
MONTANA 99-on 15 X 6 5X115 12mmX1.5 70.3 H
TRANS SPORT 90-97 15X6 5X115 12mmX1.5 70.3 H
 
Buick
REATTA 88-91 15 X 6 5X115 12mmX1.5 70.3 H
REGAL 88-96 15 X 6 5X115 12mmX1.5 70.3 H
REGAL T-TYPE 85-89 15 X 6 5X115 12mmX1.5 70.3 H
RIVIERA 93-96 15 X 6 5X115 12mmX1.5 70.3 H
RIVIERA (T-TYPE) NO FIT-!! 86-89 15 X 6 5X115 12mmX1.5 70.3 M
RENDEZVOUS 02- 15 X 6 5X115 12mmX1.5 70.3 H
LE SABRE 86-96 15 X 6  5X115 12mmX1.5 70.3 H
 
I made this list while trying to find OEM steel wheels for my 1992 Oldsmobile Delta 88 Royale.

Of course I can't guarantee that all these will interchange due to things like brake rotor sizes, but it should give you a good starting point when searching the salvage yards or wheel dealers.

I appears the Delta 88's did come with a 16 inch wheel option too.