OK, from the book Century Jets( itself a compilation of AIRTime Publishing magazine articles).
the prgramme, called Thunderstick II, applied to D and F models. it involved installation of AN/ARN-92 LORAN and put solid state components in the NASRR radar system, now being designated R-14K. with these systems a Thud pilot could reasonably expect a CEP of +/- 50 ft from and altitude of 15000 ft
they were easily distinguishable by teh large dorsal spine to house the LORAN and Doppler equipment. at least 30 d models were modified.
although designed to help the crews in Southeast Asia, none of the Thunderstick II aircraft left the US. they were assigned to the 563d TFS, 23d TFW at McConnel AFB KS; then transferred to the 457th TFS (AFRES) at Carswell AFB TX remaining until 1980 when they were replaced with LORAN equipped F-4Ds
NIELS top pic would be the 563d TFS, his bottom pic would be the 457th. dig a little deeper into pics on google, as Guard/Reserve units tend to change fin colors by flight (four aircraft) rather than squadron (18-24 aircraft) like the Active duty folks