Hopefully the daughter missed the decimal point and it’s only 1000 hours. While a diesel generator is good for 20,000+ hours that’s a lot of use on the rest of the rig. On IRV2 there are posts about the ISX dropping the #6 intake valve to the tune of $25,000+ in damage. Mainly ISX in RVs, not trucks and while the cause is unknown, it may be related to the EGR. If so, a 03 engine does not have EGR and may be how it’s made it to 158K as some with EGR did not make it to 36K miles.
As you can see below I’m a fan of the big Monaco’s and I would look for a 04-06 Executive with the Detroit 60 engine. Our Snowbird park mandates that we had to go to a 08 rig or newer and Monaco stopped having a Detroit as an option by then...I have a ISX 525.
The chassis is the same between Dynasty, Exe, and Sig with more bling and fewer non standard options in the Exe and Sig which have bigger engines.
