P-51D with additional radio equipment in place of fuselage tank?

For a long time I thought all P-51D (and K) Mustangs were produced with the 85 gallon fuselage tank, however at least two flight manuals make reference to early P-51D aircraft without the rear tank, but more radio gear in its place:

AN 01-60JE-1 Pilot's Flight Operating Instructions P-51-D-5 and Mustang IV airplanes

AN 01-60JE-1 Pilot's Handbook for Models P-51D and K series airplanes

Also this bit from Wikipedia (emphasis added by me): "P-51Ds without fuselage fuel tanks were fitted with either the SCR-522-A or SCR-274-N Command Radio sets and SCR-695-A, or SCR-515 radio transmitters, as well as an AN/APS-13 rear-warning set; P-51Ds and Ks with fuselage tanks used the SCR-522-A and AN/APS-13 only."

My question is how many, if any, P-51Ds were produced in this configuration or if it was a modification only?

Thanks