Have twin 525's with 250 hours on them. Any reccomandations on rebuilds with whipples.

I recommend you set aside about another 20k for drive upgrades if you add whipples.

There is no need to rebuild the entire engine, but I would certainly do the top end before adding a Whipple. We have done a bunch of Whipple installs on 525's and it's a great piece. You really can't go wrong. However, the valvetrain is not the best on the 525's and must be upgraded before the added stress and rpms. Exactly what need to be changed will depend on the year of the engines. What year are they?
Eddie

The engines are 2006 first gen 525's.

Eddie, on a dozen or so 525efi's builds, didn't have one that did not have a tight piston to pin in at least one cyl.. Have you run into that much? I have talked to friends at Merc racing , and of course they said they never run into that, and of course they wont admit that putting a pressed in pin was to cut $$$... LOL