I converted my Avion 34X (actually a 36 footer measured bumper to ball...it really is the Long Long Trailer....) from 30amp to 50amp and couldn't be happier with it. It's not that hard, but you'll need to be pretty handy at wiring.
I used a Progressive Dynamics PD4560 power station. It's 60amp.
Ultimate All-in-One 240V, 50 Amp AC/DC Power Distribution Panel
I had to do some carpentry work. The new power station was taller, but narrower, than the OEM unit. It was also about a half inch deeper. So after labeling all the wires, disconnecting them, and pulling the old unit, I held the wires up out of the way and cut the cabinetry to make a taller hole. I then glued and screwed a couple of wooden filler pieces to make the hole narrower. I then cut a piece of 3/4" plywood, beveled the edges, sanded it really smooth, painted it black, and installed it over this hole to make the spacer that would set the unit 3/4" closer to the center of the coach and allow it have enough room depth wise.
OK, next biggest issue is running the main feed wire. On my trailer, the power station is on the curb side and the "power door" is on the street side where you'd normally plug in. I ran a 6awg wire from the power station through the cabinets forward until I was abeam where the power door was on the other side, then hole sawed a hole in the floor to drop under the floor, cross the floor, then pop up on the other side with another hole-sawwed hole on the street side, under one of the dinette seats. Then a hole through the side wall under the seat into the area where the power chord used to be stowed, just inside the "power door." I used foam padding at all holes between the hole and the wire. I used pieces of nylon strap and screws to hold the 6 wire in place (it's roughly the diameter of your arm but you need 6 wire for 50amp and not very flexible). I wired the standard female 50amp receptical end onto the end of this wire. The standard 50amp RV connector has the male end to plug into the campground tower and the female end to plug into the RV.
OK, next bundle of fun was the "bowl of spaghetti" that was the 120v ac wiring and the 12v
dc wiring from where I threw the old Univolt over the hill and got the new unit. Hopefully you labeled all of these clearly before disconnecting. It wasn't hard, just tedious. All the 12V
wires hooked up to the power station's fused 12v
leads (got modern blade type fuses at NAPA). For the 120v ac side, you need to get new breakers to fit the box. I used GE breakers I got at Lowes...same time I got the 6 wire...and always buy 2-3 feet more than you need....you can always cut off and throw away excess wire...don't want to splice something that heavy....). Just take your time. Also, you have two bus bars with the 50amp circuit. So you want to make sure you split up your big draw units between the bus bars. For example, if you had two air conditioners, you'd probably want to put one on one bus bar, and the other on the other. I don't recall exactly how I did mine, but I split them up so that both buses got about the same draw and neither bus was overloaded.
See, with the 50amp setup, you have two feeds times 50 amps. Compare this to the 30amp setup where you only have one feed times 30 amps.
So with a 30amp, you get 30amps times 120 volts = 3600 watts of power available.
But with a 50amp setup, you get 50amps time 2 buses times 120 volts = 12,000 watts of shore power available.
Whereas before we could have a/c, the microwave, and that was it. Or a/c, the hair dryer, or that was it.....you get your choice of any 2 of the big 3 draws.... With 50 amp you can run 'er all, all the time, and smile.
Somebody wants to rough it, get a tent and let the bugs chew on you.
You want to glamp, set up a silver tube with 50amp and be happy
For me, the PD4560 works great, and I highly recommend it. Their unit has what they call the "Charge Wizard" and it works like a "Battery Tender" where it actively senses what charge level your batteries are at, what they need to stay topped off, and when to back off so you don't overcook them. My old univolt would BBQ the batteries. The Charge Wizard keeps them nice and full without BBQing them.
The only drawback, and it is super minor, to 50amp, is that the chords are expensive and harder to coil than the skinny (by comparison) 30amp ones. I got a couple of nice big plastic tote containers from WalMart that fit under the dinette seat and keep them in there. I have a 50' chord and a 25' chord, as well as a 30amp to 50amp pigtail. These go in these two boxes and work just fine.
Do it. You won't regret it!