Check this post out, camaros.net
The "FW" is a 'JJ' rim profile 15X7" rim with a .30"* offset.
GM #3997899 (Group 5.803) with applications from 1969 ~ 1975.
Listed as a service replacement for part #3970531 wheel for 1969 Camaros w/Disc Brakes Front and Rear (RPO-JL8) and w/ 302 option (RPO-Z28).
Listed as a standard or replacement wheel for 1970~75 Monte Carlo and 1974~75 Chevelle (exc. wagon).
Welded construction, 4 cap projections and Tubeless rated.
Code you gave may be missing a number or two - but, looks like a Kelsey Hayes Rally from the Romulus, MI plant manufactured in ? (1975?) on
*Some conflict in GM documents about this - measure the 'backspace' and see if it isn't slightly more than 4 1/2".
Hope some of this helps;