I run 37s (13.5) Toyos with Frankies 3.5" and 30mm spacer comfortably......and previously fit 38.7 michelin xmls with same setup. (rear fenders trimmed up to wheelwell lip and fronts to match. plenty of clearance and basically stock plushness on road/ highspeed fireroad chop)
Id say if you are under 5800lbs.........and you want a more plush ride- this may be a solution to rattly teeth and dental work
ive run these springs between 5000 and 5700lbs and perform great in both and ideal in the upper half of that weight range imho