69 Notchback Mod Top $5000 Illinois. Marketplace NOT MINE

So your 383 cuda is a formula s(obviously) but came originally with 383-s ? No fish? A53?
Love the 71 too!
I would say the proof would have to be very convincing to say a non A53 fender tagged car is a Formula-S. Mamopar has made mistakes and theoretically could miss the A53 on the fender tag.

The dealer could have installed the Formula-S stuff to make a "clone" from day one, I guess.