A VIN "decoder" seems pretty useless considering that the VIN numbers on these cars are so simple that I can explain all the variations in a few lines...take these prefixes and then tack the production number ###### onto the tail end of it and you will have your full VIN.
GRS30-RHD 260z 2+2
GRLS30-LHD 260z 2+2
GHS30-RHD 280z 2+2
GHLS30-LHD 280z 2+2
Yes, same VIN prefix for both 240z and 280z...confusing, isn't it?
You can see a full breakdown of all models here...