Is it possible to change the hub on rear beam from drum to disc without changing the whole beam
Yes. But you have to put the entire trailing arms on which by the time youve cocked about replacing the bearings while removing trailing arms you may as well of put a beam on it.
You don't need to change the arms, just the stub pin bearing and backplate.
I wouldn't bother though, drums are more than adequate.
Yeah just smack the stub pin out and disc one in.
Lol. I didnt do it like that. My bad.