Did they make a 7.3L f450?
Yes, up to an F550. 2003 is the last of the 7.3L. 6.0L came in at 2003.5. I'm not sure I'd buy one. People do buy them, throw $5k to "fix"' them and then I see them sell them 1 or 2 years later. Odd... I would avoid the 6.0L and 6.4L PowerStrokes if it was my $. The 6.7L is intriguing but I'm not sure how I feel about it yet. Total clean sheet of paper vs the International engines before it. Definitely impressive to drive but how are they with miles on them? Time will tell. 7.3L are going up in price, not down.
The bad thing about that is they aren't getting any newer. You'll pay for a lower mile 7.3L and they really aren't all THAT impressive. They just work and work well. The truck they are wrapped around is a solid truck. Decent engine in a solid truck. You'll get good at changing CPS sensors (I did, anyway) if you get a 7.3L. They are semi-reasonable on fuel, decent on power and pretty dang reliable. Just aren't getting any younger.
Turbo's, injector pumps and injectors can bite you at any time with any diesel. Transmissions and clutches (and sometimes rear diffs) take a pretty good beating from the torque.
I've weighed in at 24,400 with my flatbed V10 F450 manual... Super cheap tow rig ($5k), handles the weight no problem... Just not fast, and single digit mpg.
single digit mpg in my F250 as well. Mine's a '99 and is not fast, but grunts well and likes fuel. No turbo, injector pump or $250 injectors either.
How reliable are the v10s? I heard they spit plugs
I think that is a LOW percentage. Any of the earlier modular Ford motors only have three threads holding the spark plugs in. Happens to the v6, 4.6L and 5.4L v8 as well. I think they fixed that in '01 or '02? The later model V10 is a 3V per cylinder ('05?). They run WELL but get the same mpg as the older ones. Since I've gotten our V10, I've been pretty impressed with how many miles some people have on theirs. Ours has 225k miles and still runs quite well. It has a lift and could use some gears but I'm not sure I want to even work on it to get rid of the lift and/or gear it. I think it would tow very nice if geared correctly. I top out at Soldier Summit at about 60 mph. Pulling out of Moab as the grade increases from Arches park gets me down to about 52-55 mph.
For what you sound like you're using it for, I'd get a $30-60k motorhome and buy a $5k enclose trailer to tow behind it. Might be cheaper than the toyhauler/truck combo? I think the upkeep on a motorhome would be similar to a pickup/fifth wheel? They are both like having a house made of uber cheap materials. You will have a list of things to work on no matter how new the RV is.