With the 480R rated at 48,000 psi (NOT Cup), the stainless steel should be adequate if heat treated to be less-than maximum hardness. That is Huntington would be able to document material and proof pressures by coupon of the finished bar stock cylinder.
Frame stretching on the Vaquero topstrap would be my priority concern as there is not alot of steel there. But again, the maker will certify the safety of his design.
Still wishing someone would make up a 480Ruger barrel for a No. 3 carbine with hunting sights (Williams, Millet, etc.) and I would take it to the dark Adirondack woods for fall bear... UNtil Ruger re-makes a 96 lever action in Bill's namesake chambering, that's all I can do!