yo found this, why not do ctr pistons to get higher compression? more power if you going all motor.

PR3 head/B18A/B Block

STD = 12.825536009218106
.25 OS = 12.88971493738735

P72 head/B18A/B Block

STD = 13.170743903246784
.25 OS = 13.236528215133324