Maybe, maybe not. Squirt a few teaspoons of engine oil through the spark plug hole and recheck. If the pressure remains the same, the problem could be valves, valve guides, cracked head and/or a blown head gasket. And, it's possible that it could be one or more of those in combination with ring wear.

#5 cylinder is a favorite place for a 3.0L head gasket to blow. I have seen suggestions that the 2 rear cylinders don't receive adequate coolant flow, but I'm not yet certain that's the reason.

Since factory parts are becoming expensive and sometimes scarce, I've been curious to see how cheaply a 3.0L can be rebuilt and still last. For a standard rebuild, I'd be tempted to try one of the auction site kits from a seller who has a good rating, because I suspect that there may be some reasonable value there if you shop carefully. As an example, I bought lash adjusters that normally sell for ~$12/ea for less than $5/ea and expected to get some cheap knockoff - but they were made in Japan and distributed by Sealed Power division of Federal Mogul. They look and perform like the original. I'm not suggesting that is the norm, but that some of the kits may be decent.

If you find a good kit at a reasonable price, please let us know.

Frank