They should be a direct fit FWD and FWD. That said, I ran my X1/9 wheels on my Yugos for years and they stand out quite proud so the 500 FWD offset should tuck them in nicely. As Karl says though, you may need spacers but if I had to bet I would bet they fit with just the factory 5mm spacer.
When I had Yugos and considered 500 wheels the 14x6 was my wheel of choice Tirerack has a great selection of theses wheels at pretty fair prices.
I would find someone I know with a 500 and do a swap and check clearance.
Let us know if you do go that way I will do likewise.
Regards