Do you still have these? I picked up some STI HD wheels and don't have the right size lug nut either. I just bought some extended 60mm 3/8x24 that don't work either .My guess is that the lug nut fits, but the socket you need to turn it isn't big enough to fit in the wheel? If so, what size socket are you using?
We have lugs in stock that use a 14mm socket, would that work for you? If so, cost on them is about $5 per wheel, plus shipping.
Give me a call if you'd like to get a set rolling.