ford f250

Well people kill bears with .22s but I won't plan on it. I want something larger more powerful.
All kinds of ways to increase towing and stopping power.
If your axle is heavy enough, and I don't know if the axle with the 351 is the same a diesel or not . If you can find a used diesel differential axle brake, for a wrecked or scrapped vehicle would be good. The gear ratio might need changing in the speedmeter. Same with the trans. If you want to stick with gas Ford has crate engines up to 570 inches I was told, but certainly some over five hundred inches. And a heavy duty tans, radiator and oil and trans coolers. and changin brackets etc for air and brake booster. Probably 20,000.00 or so.
There are or were companies that specialized in installing diesel engines and drivetrains in gas pickups. I looked a t a couple of laces when I had an85 Dodge 4x4 but never did any changing.
You can haul it with the 351 but it will be strain and over rate for your truck and in some places perhaps a ticket.
Perhaps you can find a decent07 or earlier Dodge Dualie Diesel with no cats nor no pig pea tank. Almost bought one two years ago with 7,000 miles on it with fifth wheel hitch and everything for 27,000.00 or half a new one.

hill,s is really not the issue, l have been pulling a 35 foot with 16 foot slide out with my other truck a 96 ford f150 extra cab 4x4. then l bought the 95 f250 extra cab 2 wheel drive long bed. l pull it back and forth to the river about 30 to 40 miles away. then l just bought the 2000 28 foot 5th wheel and people is telling me l have to have a diesel. now it has me second guessing myself. l havent use the f250 to pull it yet cause l am having the 5th wheel hookup installed on it. Thanks for all the help.

Keep the trailer GVWR within your tow rating for best results.

Is the 7600lb trailer the wet or dry weight? Is the 8200lb 5th wheel the wet or dry weight?

If dry, the 5th wheel will be pushing 9500lbs loaded and ready to camp. Your truck has plenty of capacity to hold the front of the trailer up and will get it from point A to point B. How happy and sane you are by the time you reach point B will depend on your expectations.

It'll be slow and you won't be able to keep up with traffic in the hills.

Pulling it is one thing. Stopping it is another. That is another factor to take into account, especially going down steep grades.

According to this it looks like 7800# is your maximum. That was a new truck in 1995. It is now a 20 year old truck. Is it as strong in all respects as the day it was born? Yes, it will pull it. How far and how long is the question.

Grade, length of grade and altitude can really tweak on the ability of an engine. A 220 horsepower engine that got-by pulling 6000 lbs may fall flat on its face pulling 7500 lbs. It's a rare RVer who can resist stuffing even more clothes, food, toys, and miscellenous in a new rig. Solar panels, batteries, inverters, you name it. I would ask myself "did this engine have LOTS of extra power with the lighter trailer"? How many more "young" miles does your existing truck have left in it? New trucks have loads of goodies like exyreme power alternators HD radiators, perhaps more comfortable seats, more desireable cabin layout, to tempt. From what I've seen there is a lot of suspension difference between a standard 3/4 ton and "heavy" 3/4 ton.
350 cubic inches is not a real heavy duty engine.

In the end you need to sleep on all this. A new truck is expensive and only you have sense if the truck is perhaps borderline powerful. Not an easy decision IMHO. :) :) :)

it is a 1995 super cab long bed 2 wheel drive

What year is the truck. Which cab? Is it a 4X4?