What should the center to center distance be for rear shocks on 348.and what was rear travel

I just measured the original Telesco shocks from my 1976 Cota 348. They are 360mm eye to eye.

Axle travel to the point where the shock body just touches the bump rubber is 114mm.

Axle travel to compressing the bump rubber 10mm is 129mm.

You asked what the shockie length "should be". All I know is what works for me. I have 1980's vintage Marzocchi shocks on my 348. They are 352mm eye to eye and still work great.

If I needed new shocks for the 348, I would buy Falcon Classic Trials shocks without hesitation.