What you are describing sounds like a screw in aftermarket stud. Can you look behind the axle flange to see if the studs screw in or press in? Some aftermarket axles have provisions for screw in, 5/8 lug studs to eliminate the mag wheel lug nut that centers the wheel on the nut. These style of studs are a true stud that centers the wheel on the stud then uses a large washer and nut to retain the wheel to the studs. Actually a much better, and stronger, arrangement than traditional mag lug nuts. The problem you will have is these style of studs are designed for thick, lightweight, competition wheels. Stock style rallyes use small acorn style lug nuts and are thin pressed steel that do not have as much contact area on the lug nut as the competition style you have. Basically, as you noticed, stock wheels are incompatible with competition studs like you have. What you may be able to do is see if you can identify the axle manufacturer, call them and see if they have the correct stud style for the mounting the stock rallyes. This also means if you ever want to put yout lightweight wheels back on, you will need either to change the studs, or will need to buy all new lug nuts to be compatible with the new studs.
