Also, unless you add a spacer between the UIM and LIM, the UIM for the 2.5L heads will not fit the 3.0 because the 3.0 Valve cover will get in the way. So, you must either have a custom spacer machined or you must modify either the 2.5L UIM, or use the 3.0 UIM & LIM and get a hood buldge/scoop fitted because the entire 3.0 longblock will not fit because the UIM will hit the hood about 1-2 inches from closing. I would opt for a rebuilt 3.0 Longblock with a nice hood scoop ... this will help keep the heads cool, just have to accomodate for water pooling in the spark plug gallies because this will cause them to rust in place. By scoop I mean Impreza sytle hood scoop to cover the hole you are going to have to cut into the hood to accomodate the 3.0 UIM.
I was under the impression that you would be trying to use the 3.0 heads but wanted to know if you could/should use the 3.0 UIM. Perhaps I missed something. So you plan on doing a 2.5L/3.0L hybrid correct? If that is the case, then the 2.5L heads will clear the UIM and you have nothing to worry about. However, if you use the 3.0L Heads and Block, it would be best to use the 3.0 UIM with a modified hood as opposed to spending the extra money to modify the UIM or have a custom spacer built. The money saved could go towards the tri-metal bearings.
At this point, you would be doing a 3.0 Longblock with the 2.5L oil pan and pickup tube ... a lot less complicated to install with less downtime. I recommend this not only for these reasons, but also because I would never use JB-Weld inside the engine, which is what everyone is doing to plug the gallies that don't match between the head and the block. The proper way to block these gallies is to weld them shut and then redeck the block ... a lot more expensive, but done right with 0% chance of anything dislodging and killing your motor. JB-Weld "could" come loose if not done correctly and even then, I still wouldn't trust it. Besides, nobody to date has tried the direct swap of the 3.0 (almost direct, the 2.5L oil pan & pickup tube needs to be used), or so I gather from my research on the subject.
