Good Advice and I'd say that you should consider DK-50 1:1 which was a Kodak recommended developer for this film of this era. I'll go against the grain Ha and say you'll probably end up shooting it closer to 250-320 in DK-50 1:1. I was gifted a large stock of Plus-X Pan in 120 from this era and ultimately I thought it looked best in DK-50 1:1. I believe D-76 1:1 times worked well. More modern developers like Xtol and Ilfosol sometimes would barely produce an image where as the DK-50 1;1 was a robust neg, I had to expose closer to box speed than I was with the modern developers. It had lost less speed than I was expecting and once I dialed in a better EI the DK-50 negs were top notch with the lowest fog tested.
I recall a Tri-x formulation shift just before this stock of film was made so this would have been the stock I would have been using through the 1980's into perhaps at least the mid-1990's. I used hundred foot rolls weekly at the newspaper and to keep my darkroom time interesting I would swap in a 100ft roll of Tri-X instead of our standard Tmax 400 so I got to know this film in 35mm and later on in 120. There used to be an additive that you could put into D-76 and would make Tri-X go to like 12,500-25,000 easy but had massive grain and no latitude. At some football and night baseball games you could really dial in the exposure/development to match what the presses could do and it was always a sweet feeling when I'd open up a fresh copy and see my shots reproduced well. Back on topic...This era of Tri-x had more grain than the next one, which was the one previous to the one on the shelf right now which undoubtedly has T-Grain emulsion in whole or part. My personal EI for this in 35mm was 640 in Tmax developer but I was always in lower light and printing a too dense neg was much less desirable. Good old D-76 at 1:1 was and is a solid standard and I would think the OP would be wise to at least do one roll in this old faithful combination. The good thing is that you have 5 rolls and you can use one as a test and do two batches of two rolls pretty easily. Good luck have fun