I did all of this research about a month ago and ended up buying the Moose Utility Division 1.5" wheel spacers (p/n 0222-0432) off of Ebay. I looked at the SuperATV spacers but if I remember correctly they were only 10mm studs. There are a lot of spacers out there but 99% of them seem to only have 10mm studs... I paid just under $200 for all 4 which isn't horrible I guess and the quality has been good so far.
Note- I always use loctite on the factory studs when installing spacers and have yet to have an issue with them on the Wolverine or on my old Grizzly.
Well spacers arrived and they are wrong. 10mm studs. Just got off the phone with Casey at Superatv and he confirmed that they are in correct. In fact they do not make a set of spacers for the rspec or the Viking. The ones that were send are for a wolverine 4 wheeler. Just my luck. No waiting on return tag and refund.