1969 Lynch Rd. is all B-body (non-Charger)
so, the available "performance" tires were:

F70-14 red (Goodyear SPEEDWAY or Firestone WIDE OVAL) - "F70 R" makes sense
F70-14 white (Goodyear SPEEDWAY or Firestone WIDE OVAL) - "F70 W" makes sense
F70-14 red POLYGLAS - "F70 X" is the F70-14 red POLYGLAS as the OP's car is a GTX & the RWL tire was not available
F70-14 black w/RWL POLYGLAS (spring special Road Runner & Super Bee ONLY) - "F70 B" is the F70-14 black w/RWL POLYGLAS - is the car a "spring special" Super Bee?

F70-15 red POLYGLAS - "F70x15 R" makes sense
F70-15 white POLYGLAS - "F70x15 W" makes sense

G70-15 red POLYGLAS (A12 ONLY) - "G70x15 R" makes sense

thoughts? any broadcast sheet or window sticker VS. trunk lid confirmations/comparisons?