Kodak hasn't made Plus-X in 4x5 for a long time, so I'm thinking your film is way past expiration. Still, Plus-X is pretty sturdy stuff and should be fine if it's been stored cold.
I'd proceed by using the recommended times in the current documentation for the film. There have been some slight adjustments over the years, but from what I've seen they have been well within the margin of error for the home user. Use the times given for rotary processors on page 4 of
this document and adjust from there if necessary. Should be just fine.