The correct ones to use with the alloy wheels (IMHO, including Rivieras!) are about 2.5" long total. The lug bolts for steel wheels are only about 1.5" long total. Sounds like you may have the steel-wheel version.
Used bolts are often pretty pricey. There are "almost right" ones that go for a medium amount of $$ (they have a 17mm head instead of a 19mm one, but they are the same otherwise). Check the ads here and on 914club for used stuff like that. Or buy new from Pelican, of course!
--DD