RS in VIN# tells you it's a GTX
if the last 8 digits of the VIN# number match the core support and trunk lip, then the body matched the VIN# & it's a GTX.

STD radiator in a 440 and/or 440+6 GTX with an automatic is 22".
You need 4-speed, A/C or an axle package for it to be equipped with the bigger radiator.