if you put 2.5 heads on a 3.0 you end up with a 11.2:1 CR, so 93 octance or better becomes even more mandatory than in an SVT motor.
The oil passages that need to be filled, are two drain holes on the back of the motor (that means transmission side) and one oil supply hole on the right front of the motor (belt side). These holes need to be blocked because the cooresponding holes are absent from the 2.5 heads. If you get a set of 2.5 heads and set them on a 3.0 block, you will be able to tell which drain holes need to be filled, because the heads do not completely cover the holes. I do not have pictures, but they are available someplace on the old forums.
Tuning is a good idea anytime a major change is made to the air flow demands of a engine in order to keep everything in check and safe. You may be able to simply put on an adjustable reg, turn up the base pressure and keep fuel supply adequate, but with increased compression, and the change in displacement, spark timing may not be optimized and you may still run into runtime problems without having the ECM tuned. That being said, I know that more than one individual has put a 2.5/3.0 hybrid motor setup together and run it on the factory tune, but it is not the "best" way to go.
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87 Mustang GT Turbo
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