I found pictures of the Superbird my Uncle owned when new. One thing that stood out to me instantly was the steel wheels and dog dishes. I was just wondeding is there a number or educated guess on steel wheel cars , they do not seem near as plentiful as Rallye wheel cars , Thanks

A bird can come with 14" or 15" steel wheels. Most probably had the 15" Rallye wheels.

Both my brother and a friend of mine had 440 automatic Birds, yellow, with 14" steelies

1970 RM23 numbers which include the Superbird (I doubt Superbird varied significantly from this data) 15" wasn't that popular

tires:
T86 F70-14 "White Streak" STANDARD ~ 41.1%
T87 F70-14 w/RWL ~ 50.9%
U84 F60-15 w/RWL ~ 7.8%

wheels:
hub cap STANDARD ~ 12.6% (14" & 15")
W11 deluxe wheel cover ~ 14.0%
W15 wire wheel cover ~ 1.9%
W21 RALLYE Wheels ~ 36.0% (14" & 15")
W23 ROAD Wheels ~ 35.5%

ROAD Wheels & F70-14 w/RWL POLYGLAS tires is the most plentiful installed choices