I'm thinking of new wheels/tires for the van.

I've now got a very old set of Ronal mags, and they seem to have all sorts
of  numbers on them - I'm hoping there is a standard numbering system for
aftermarket wheels that will allow me to choose replacements (most likely
used) without the "yeah I think it'll fit " uncertainty.

1) is there a standard numbering system?
2) if there is is, then
what is the bolt pattern description for the van?
what is the range of wheel widths useable?
what is the offset useable without using spacers?

anyone have definite answers ? ( yes I know that generally BMW/Mercedes
wheels will fit, but I'd like to be a bit more specific if possible when
looking)

Bill M
'82 GL I4