How much spring you will need is in part dictated by the shape of the cam lobe (profile) and RPM. You could always go to a little less rearend gear also,lol.
if i can go faster with the 4.88's why would I?? i never go faster than 45mph anywhere i drive anyways where i live so it dosn't matter... and i live 25 minutes from the track...
and yes i know spring pressure is based on ramp slope, engine rpm, boost, and some other variables...
EDIT: may go higher if the car likes it... will up to a 30 or 31" tire as well though...