We are looking at a possible used gas Class A motorhome purchase in the next few months, likely 2002-2005 model years. Any opinions/observations on on the 6.8 Ford vs 8.1 GM motors in regards to maintenance and reliability for these years?

I prefer the 8.1, but only because I've driven it. Drove it in a suburban 2500 pulling a 12k trailer and it did great.

They will both drink gas though. Quickly.

V-10 is a dog.

I have the 8.1l, it seemed more people prefer the workhorse chassis - not just for the motor. The V10 revs higher to produce power, the 8.1l has more torque at low RPM. In 2006 the workhorse moved to a six speed transmission, my 2005 has a five speed. Not sure how desirable the additional gear is but mine does fine. Nearly all our trips are within 3 hours so it does fine for us, we've taken it a couple times to Colorado, flat towing a vehicle, with no issues. A diesel is better but not necessary for our use, I would love diesel just to be able topull straight through the diesel pumps as opposed to having to wedge in to some difficult gas pumps.

I've put a lot of miles on a 2004 V10 F250 and it's a good motor, but is a dog at high rpms, but very torquey down low. The 2005 model year is when they switched to the 3V head design and it's supposedly a better performer.

The only 8.1L I've driven have been in the big uhauls and they do really well in those for such a large vehicle.

There's no replacement for displacement when you're talking N/A truck engines and I'd go for the 8.1L if I was buying a big gasser right now. Not crazy about smaller motors that have to turn 4K rpms to make torque when I'm towing. Although the V10 has impressive torque, based on my experience, the 8.1L has more. Fuel economy is going to be terrible either way.

I have the 8.1 in a 2004 Fleetwood fiesta 32s. I haven't yet taken it in the mountains, but it has plenty of power at low RPM's. I have had diesel trucks, but never driven a diesel class A. I'm pretty much able to do all of my own maintenance on the gas engine. I've heard horror stories about the maintenance on the diesels.