The only notable differences that I know of between the Grumman F9F-2 and -3 is that 1) the -2 was powered by a P&W J42 engine and the -3, an Allison J33 and 2) the -3 with the J33 engine was never modified to carry bombs or rockets as the -2 was. The -3 was delivered first, to VF-51 to replace their FJ-1s. The picture above was taken during carrier qualifications aboard
Boxer. Only 54 F9F-3s were produced; most had the J42s substituted for
the lower-thrust J33s and were redesignated as -2s. According to Baugher (
http://www.joebaugher.com/navy_fighters/f9_3.html), the changeover was accomplished in October 1949; however, that may have been when the first ones were converted because VF-51 and VF-52 were reportedly at sea with them in 1950 off Korea.
The earliest F9F-3s and -2s also appear to have a slightly different ejection seat headrest. See
http://tailspintopics.blogspot.com/2016/03/early-us-navy-ejection-seat.html
I'm therefore not sure whether VF-51 deployed with -3s per se. It and sister squadron VF-52 were aboard
Valley Forge in the western pacific in mid-1950, just in time to be in on the start of the Korean War. LT(jg) Leonard H. Plog of VF-51, reportedly flying a -3 (BuNo 123071, modex 109S), made the first carrier-based jet kill, a North Korean Yak-9., in July 1950
A picture of VF-51 F9F-3s, according to the caption, deployed aboard
Valley Forge is provided below. Note the lack of "Navy" and "VF-51" on the side of the aft fuselage, the unusually large number on the nose, and the large "104S" under the left wing. The later markings would be smaller and in addition to "Navy"and the squadron identification on the fuselage, there would be "Navy" on the underside of the left wing. The erosion-resistant leading edge treatment (see
http://tailspintopics.blogspot.com/2012/01/corogard.html) on the leading edge of the wing, inlet, tip tank, and empennage is also clearly less wide on these F9F-3s:
Hobbyboss has recently released a 1/72 kit of the F9F-3. I don't know if they have corrected the errors in their F9F-2 kit (see
http://tailspintopics.blogspot.com/2011/05/172nd-f9f-2-panther.html). Markings are provided for VF-51. However, VF-51 made a second Korean war deployment, only in -2s aboard
Essex, and it appears that the markings in the kit are those of VF-51's F9F-2s, not its F9F-3s. In the photos I've seen so far like the ones above that are definitely VF-51 F9F-3s, neither "Navy" nor "VF-51" is marked on the aft fuselage. In a movie clip, I did note a red area at the top of the fin and on the nose, unlike the above. F9F-3 109S reportedly never got a kill marking, either, as shown in some illustrations. (See
www.history.navy.mil/nan/backissues/1990s/1997/mj97/plog.pdf)
In any event, the stores pylons should not be used; the J33-powered F9F-3 were never modified to carry rockets as shown on the box art like the -2s were.