It's been 30 years since we sold these barrels, the big white gasket , the white rubber o ring has gone.
If that's perished then it's a goner.
The plates don;'t usually wear out but if they're missing then it's met it's end.
The tap , valve and float are all replaceable and the modern bits still work.
You'll need the combined pressure relief with with collar, you just take the collar off and it works.
Floats are interchangeable and the drum tap fits.