Hahaha, an XWX question! The carburettor 308's, so from 1975 to 1980 all came with 14" wheels and XWX's as standard. 205/70-14. Standard rims were the same as the W116, 6 1/2" but optionally uuo could order 7 1/2" with the same size tyres.
Here is my 1976 carb car with them on 6 1/2" rims:
From 1977 you could order your 308 with 16X7" wheels front and 16X8" wheels rear but it was a very expensive option, the wheels were sand cast magnesium. Not many cars were delivered as such.
When the 308's went to fuel injection in 1981 the cars initially came with XWX's like the carb cars but then went to the metric TRX tyres from Michelin. The 308 GTS above is pictured with the original 220mm/55/390mm TRX's on. I have since changed the wheels to 16".
Yes, the 308 is a really lovely looking car. It's best in silver or blue I think. I think the coupe (GTB) looks better than the GTS (Targa top). This is my carb car with the later 16" wheels fitted for a track day.