I have a '76 504 LTi and I would like to fit original Michelin 175 14 XAS tyres. They are advertised as still available in the UK, any clues about local supply?
If you proceed with the Xas, I suggest not parting with money before you have evidence of a manufacturing date of less than 18 months.
The other option is to accept mild undergearing (3.2%) & fit 185/70. Michelin have two offerings (the XM2+ & the Energy Saver+) & Hankook has the Kinergy Eco2. Each is around $150 fitted & balanced.
Each of these would be better wet tyres than the Xas.