[slowmover]

7.5-mpg sounds right. I'll bet it's also 55-58/mph for that. Consistent with what we saw with a bigger Moho in the 1970s. Also consistent with other carb'd big blocks pulling trailers from then. 9-mpg sounds like a nice goal.

But dropping cruise rpm may not work as well as you think. TQ is needed to maintain headway, and gearing must be effective. Keeping motor up near peak torque is how that happens.

As iv tried to emphasize, mech condition will mean most. And steering wander is what I'd attack. Slop in the column itself (rag joint) out to wheels. It's not just the steering box. (Lee Power Steering is who I used years ago on Saginaw problems. A blueprinted box is your friend).

In same way, chassis to body bushings. Rubber doesn't last forever, and fresh will keep movement -- affecting steering -- to a minimum.

I'd imagine you've read Orbywans great threads on Class C aero as some inspiration. Only approach "reasonable " to 20%, IMO.

Start with little stuff such as replacing all exterior lamps with LED fixtures. It's a safety issue. (Interior, see LEDRV; Dan). Grote or Trucklite for exterior and FMVSS approved. I'd want to convert to 7" round headlamps as on older units as LED replacement is huge gain. Otherwise, see Barry's vehicle lighting pages on altering headlamp wiring to achieve 13V at lamps. I've done four vehicles this way.

After that I'd dig into battery problems. House versus starter problems. Usually new cables and switch needed. Alternator upgrade as the old MoPar piece is weak compared to today. New grounds with braided only. There is method and procedure here which needs be followed. Dodge Factory diagram out there some where, maybe the WOODALLS thread.

Won't hurt to weigh it. Full fresh water and propane plus gear always aboard. CAT Scale. Get all four corners separate, not just axles. Mohos have a tendency to be "off" at one corner or another. Among those serious, this is an ongoing topic (handling and braking). See also Rogers blog "RV Tire Safety" and chase all his Moho tire posts.

12-13k total weight is about where a low compression big block is still a comfortable performer.

Electrical refurb is huge for reliability. AGM batteries a good choice and a compatible charger (see Randy, "Best RV converter"; no matter what's present it's probably obsolete). It's the least needed system for camping, but the main source of aggravation and the most likely to cause hair tearing and breakdowns while en route. Fuel system hoses, etc, are second.

Propane system is simple, but tank likely needs recertification. New tank not terribly expensive.

As to appliances, the stove and reefer can be used as is (past fire safety issues on latter; today's units expensive and not as well built). But water heater and furnace should really be replaced. No parts, and safety has precedence. If you are considering a catalytic heater, then get the brand which uses external air for
Combustion.

Roof AC upgrade is Coleman Mach 8. 15k unit. Lower profile.

PPL Motorhome site is who I use for all this. Reputable and knowledgeable. And that means more than last couple of dollars.

Maxxair roof vents versus Fantastic Fan. Lower profile, not just better otherwise. TV antenna should be crankdown type. Avoid omnidirectional. Wastewater tank vents should be metal, IMO.

EternaBond tape should be part of your supply kit. And RV specific sealants. Not silicone. ***Buy Bed-It Butyl Tape*** another. Captain Tolleys Creeping Crack Cure may be applicable.

FE will come. Reliability and safety are hand in hand with it.