If you pull the pan for an inspection and the problem is a clogged oil pick up by chain guides, you might as well check the last 2 rods on the crank and if the bearings are going bad but the crank is not scored badly you might get away with just replacing the bearings on those rods but you will still be faced with the chain guides. All of that can be done in frame.
The job of R&Ring the engine in my Navigator has taught me that lifting the body off the frame is the easiest way to go. It's either that or cutting the radiator support like the Excursions and F 250s for room to work in.