All the modern reloading books will tell you if the loads they show for 6.5x55 are for modern actions or for vintage small-ring's. Just use those shown with their starting points, and work up your own loads.
Can you point out the manuals that have the modern high pressure loads. I have yet to see one that goes over ~45,000 cup.
Speer data off the top of my head runs 50K CUP, Lapua (Vihtavuori) lists the 6.5x55 SKAN at 380 Mpa which I believe translates to ~ 55k PSI.
Nosler data appears to follow suit with a disclaimer it is for "modern rifles only"
