These are links to other sites that I personally found useful or interesting.
oscarmayer.net (best manuals site around. most factory service manuals and articles for maintenance or information)
3wheelerworld.com (one of the best 3wheeler sites)
wiseco.com (best pistons around. I typically use Wiseco in any performance build I do)
webcamshafts.com (Best cam shafts and support parts around for cams and valve springs Some oversized valves available as well!)
rockymountainatvmc.com (some of the best pricing for OEM and aftermarket products)
Facebook has multiple 3wheeler related groups.