Why is my ford holiday not able to turn over?

We bought a 1979 Ford Holiday and we have had some trouble with the charging system. It died a couple of times on our way home. We put a new battery in and it got us home. After the winter.same problem, dead battery. We got another new one and brought it in to see a mechanic, they put a new alternator in and it seemed to work fine
We just took it on a 2.5hour 1 way trip and back and we had absolutely no issues at all.
3 Days later we go to turn it on and nothing… The lights turn on thats it

I don't understand why it could have worked fine on our trip and now be dead.

Any help would be great
I'm desperate and devastated.

Heavy camper. What truck can pull it?

The camper weighs 8700 pd empty. What would be the best truck to pull it around? It doesn't have to be new. Something that's no older then 10 years. Ford, Chevy, Dodge? 1/2, 3/4, 1 ton?

Where did my push rod lifter go?

I have a 1973 Ford f100 with a 77' 351 modified engine, after taking off my valve covers I noticed one rocker arm was loose. We saw that the push rod wasn't touching and was about an inch and a half away and it doesn't have a lifter… And I'm a little concerned as to where it could have gone… Please help… How harmful is this to my engine.

What are some uk wide car dealers that are good please?

E.g. Ford (or other brands) used cars, arnold clark etc. Jct600 and dews are local examples for me, but some nationwide examples please, like arnold clark, that are good. Don't want websites where anyone can sell used cars, thanks.