The engine is sound. Always was a tad lumpy for the first min or so, but it runs happily on all 8 cyls and will change over to LPG at any time. At very high revs, it's not great on LPG, but normal driving you wouldn't tell the difference.
I know cam lobes are a common problem, but nothing leads me to suspect these ones have had any damage!
No easy well to tell on these....the cams are normaly pretty goosed by 60K miles and it has more effect at higher rpm....they still seem to run fine (it has 8 cylidners so if its running on 7.5 how would you know!), the timing chains are always goosed (stretched) by this point to..
Often they have low compression on one or more pistons due to the poor head design (to many bolts pull the head over to one side) which result in a slight headgasket blow into the vallley.
If you ever get stuck with one, give me a shout, I know these units very well...(I still have a 3.5 to re-build with hurricane cam and stage 2 heads etc in the garage).
The 3.5 I got had received 5K oil changes all its life and by 100K miles at strip down it had worn cams, the beginnings of head gasket failure, slight pickup on the main bearings, shot rocker gear and one hell of a slack timing chain....