We had a 1984 Holiday Rambler on similar chassis that was built about the same way as this Jayco. Flat floor from cockpit back, fiberglass front and rear end caps, integrated spare tire carrier, probably more. We sold it because it didn't have "bed down" and we no longer wanted to climb into/out of the cabover. A few observations:
Looks like chassis ("Dash") air conditioning is Factory. Easily converted to the R134A refrigerant if you need to and can't find R12 to boost it with.
Designer Series was Jayco's top line and it shows in your photos.
It's new enough to have: 16" tires and one large gas tank. Earlier was the hard to find 16.5" and annoying dual tanks
That 460 engine and C6 transmission is as close to bulletproof as it gets. Both are powerful and durable. The EFI doesn't get much better MPG than the carbureted version (like we had), but even without overdrive (like they've had since 1992) the MPG isn't significantly less than the ones with MPI and OD.
It is also a MUCH MUCH better handling (steering and tracking) chassis than 1992 and later. Yours has kingpins, not ball joints, so a lot of the Caster, Adjustable Bushing discussions don't apply to you. Luckily you don't need them. But be sure the End Links of your Front Anti-Sway Bar are a Hard, Solid, material like Urethane.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB