I remember back when the Michelins went from the XZX to the new MX in the 175/80R14 and the response wasn't way less than enthusiastic.504 suspension can be quite harsh, the IRS didn't absorb road shocks as well as the 404 live axle or the live axle on the 504 wagon. I had a 504 Ti with Michelins which had very noisy suspension, fitting Yokohama S707 transformed it, long time ago now so don't go looking for them! 70 series tyres seem to have the best ride, in between the low profile and the tall narrow.
The Yokohama's in S704/7 had a much better tread flex and even wearing tread compound. If I recall it was the tyre of choice in the VMC at the time.
The XZX use to go 'round' across the tread and in the wet was as brake effect as water ski's. This was the era of 'long life radials' to sway the punters away from cheap and rubbish cross ply's.
A slightly wider rim such as 14X6 with outward offset of the one inch.
More track is never a bad thing is it?
Brendan.