"A quick note is in order about the X-500T vs. the seemingly similar X550-P. The X-550P is called the Paladin because it was made as a signature model for Dave Gonzales of The Paladins. The X-550Ps were made in the Fender Custom Shop and while they had the same P90 Pickups and general overall look of the X-500T, the X-550P came with a Strat-like 25 5/8″ scale length since apparently that’s what the very early Guild archtops had and perhaps more importantly, that’s the way Dave Gonzales likes them. At least that’s what I thought was the case. The 2001 Price guide lists only the X-500 and describes it as a Paladin, so I’m not sure what the whole story is. My point is that this guitar has a 24 3/4″ scale neck, and not the longer one commonly seen on Paladins."
When Dave became a Guild endorser, they first gave him an (orange) X160 Rockabilly - he didn't like the pickups on it much. The next step was the Guild X500T, which was essentially a standard X500 of the time with the two duncan P90's and Bigsby/Aluminum bridge setup. There must have been some kind of mix-up at Guild (?), because for a few years the standard X500 with 'buckers got advertised as "the Paladin", while the other model (the X500T) was obviously the "Paladin" one.
I met Dave a couple of times when he was touring with the X500T, and he wasn't crazy about that either. Compared to the late 50's guitar he'd had on the road forever, the body was bigger and deeper, he had no use for the master volume, the neck pickup was too close to the neck, and the neck/body join was different so he kept putting his hands on the wrong fret. FMIC/Guild had already told him that he had the option of bringing in his old guitar and having Chris Fleming building as close a copy as possible. DG was still debating this at the time, but ended up going for it anyway, and that's what became the extremely rare X550P. Dave's still touring with the guitar Fleming eventually delivered.
The 25 1/2 scale on the 550P stems from a couple of things : Dave's first (old) X550 was a NYC made example with the long scale, his later one was a Hoboken-made late 50's one with the shorter scale. He's played strats and teles forever too, so he told me when Fleming called him to tell him he had a bunch of beautiful necks that were destined to become Artist Award necks (long scale!) and that he could use one of those, it was a no-brainer. So that explains that.
here's a clip from a Dutch TV show that has Dave's (non-master volume, interestingly) X500T when he was touring with that, it might have still been a proto at that time :