Might be a little off, but I did some measurements a long time ago when I switched my Senton to a big rock.
Senton front and rear a arms were about 87mm fron hinge pin to hinge pin. The RPM big rock arms I swapped to were about 100mm pin to pin (13mm more).
Upper senton links were about 70mm eye to eye on fronts and 66mm in rear. Thus I guesstimated the big rock needed to be 83mm front and 79mm rear. I remember it was slightly off when I finally installed it all, but that will get you in the ball park.