I don't remember what PRI I had, but here is what I used on a daily basis, before jumping over to Cyanogen.
http://forum.xda-developers.com/showthread.php?t=715915
It was a rooted version of the 1.47 update, with the most recent boot, recovery, system, userdata, microprocessor, radio, and wimax firmwares. Only the HBOOT was not updated, to keep the eng build one, so you can have an unlocked nand.
The link above assumes you have the engineering HBOOT. With the phone off, hold down vol down, and power, and look for HBOOT-0.76.2000.