Lug Studs

1968 Chevy C-10. A couple of lugs on the front wheels had broke. I bought all new lugs for the front from Auto Zone. One of them broke the other day. The wheels are not stock, don,t know where they came from. They are the 6 lug rally type. I think the issue with the braking lugs are because of these wheels. However, I think maybe the lugs I bought from Auto Zone are not as strong as they are made out to be. They are #8 lugs but I sudspect them. I look around for for stronger lugs but I don,t seem to be having much luck. Don,t have knowlage about lug nuts. I,ve had a few of these old trucks. But never had this issue. Where might I find some good strong lugs at a aforable price? And what are some things I should be aware of? Thanks, John.