I hate to hear that. They are bad in what way? Did you pull the heads and see for yourself?
If the valves have hit the pistons but didn't break then you will probably need new valves, but the pistons may be fine. If the lower end of the 3L is good, then take the valves from the 3.0 and have them installed in the 2.5L heads. It will only cost you for the exhauast valve seats and a complete valve job. Then you could salvage the whole project.
warmonger
