Tyre Size for Jellybean Mags

[RobinGi]

I have a set of mags that are stamped 13 6½ JJ
I would equate that to 165/xx 13 is this correct ?

The current tyres are 205/50 13 & 215/50 13 and I have measured the width of the rim at 195mm (outside), I would assume that the actual measurement should be the inside measurement that I would estimate at 180, would this be theoretically correct ?

I took the tyre & mag to my local tyre shop to get advice but the Neanderthal behind the counter couldn’t get past the existing tyres on the mag and would only say “can’t get them anymore”

I was hoping to go 185 80 13 to keep the circumference close to the original tyre size that I believe is 165 90 13 ?

Can anyone advise if my ramblings are correct ?

[Cal]

I've got 185/80 -13 tyres on mine, and they are indeed the closest you'll find in circumference to the original tyres.