If you are converting OEM rotors to hubs, then the longer stud is Dorman PN 610-323 Qty:10
However, if you are using new aftermarket hubs, then the holes for the wheel studs are sometimes larger and you need another stud option. Here is a side by side of the stock fiero wheel stud and the one from the aftermarket hubs with the larger shank:
So if stock fiero wheel studs don't fit the hub hole, then use this part number: Dorman 610-427. It has a stepped shank and will fit the hole in the rotor while still retaining the M12-1.5 thread pitch.
Here is what these studs look like installed. Notice it has slightly more than 1 7/16" threaded length, but more importantly notice the protruding shank:
To use these wheel studs you will need to bevel or enlarge the backside of your brake rotor holes so they slide over the enlarged shank.