Willow Flat CG on the Island has a couple of sites suited to an RV, but many are more suited to tents, which is mostly what you'll find there. Of the dozen sites, the first one on the right is a pull through about 60'+ long. If it happens to be a windy day, the wind seems to funnel right into this CG. Pit toilets, no water. IMHO Dead Horse Point is a better choice, although it gets booked early. Another option up that direction is Horsethief BLM CG 12 miles up from US 191. No water, pit toilets, but many of the 56 sites are big enough for RV's. I think it has a better setting than Willow Flat in the park.
Squaw Flats in the Needles is a different beast altogether. More than two dozen sites, many of the sites are 40'+ long. We stayed in one once that was 100' long! There is water and flush toilets. BUT, it is very busy and a very long way from town. The best bet is to get there on a Sunday morning and hope something opens up. There is limited boondocking on BLM near the entrance, but they've closed a lot of that area over the years. Hamburger Rock is a BLM camping area with a pit toilet a few miles before the NP entrance. Nice setting, but exposed with only Hamburger Rock providing any protection. There is also a private CG (Needles Outpost) you could use to stage an entrance into Squaw Flats. If you have the time and are looking for solitude and darkness at night, Squaw Flats is your place. BTW, unless you can hike long miles, you need a 4X4 or mountain bike to see much of the Needles.
Ken & Allison
2 Camping Cats (1 diabetic)
1996 4Runner, TRD Supercharger, Edelbrock headers
2007 Fleetwood Arcadia, Honda EU2000i
4 mountain bikes, 1 canoe, 4 tents, 8 sleeping bags, 2 backpacks
(You get the idea!)