Paint a decorated one. No stripping needed - pick a paint scheme that is low on graphics.
Get some "sanding film" (Testors, I think), which is very fine sand "paper" and remove
or reduce things like numbers on cab sides and other thick-ish paint/ink.
One of the magazines - MR, I believe - had a paint article about 10 years ago in which
the author made a very good point about NOT stripping a diesel (or other) body (rough quote): "the factory paint makes a better primer coat than anything you are likely to do yourself".
Obviously, common sense is important, as in all other things:
- few graphics on old paint scheme (to cover/hide/be texturally visible from a bad light angle)
- paint over old scheme with flat gray (typically) primer
- test new paint on old paint (a small patch) for compatibility, even though you're going to prime it - things can sneak through thin patches
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Once you get it gray, it's undecorated - so press on.