Hello John:

Since the pt wood you are thinking about using is 36 years old, I caution using it, and below is why.

Of course, the primary concern with using pressure treated wood in raised-bed gardens has been with the arsenic in CCA- (chromated copper arsenate) treated wood. This publication from Pennsylvania State University does a good job describing the risks of using both CCA-treated wood as well as ACQ- (alkaline copper quaternary) treatedwood: Environmental Soil Issues: Garden Use of Treated Lumber

With regards to CCA, they state, "Although the plant and human health risks from garden uses of CCA-treated lumber appear to be extremely small, there are steps gardeners can take to further reduce any such risks."

One of the steps they recommend is to use wood treated with
ACQ -"This is an alternative wood-treatment chemical that contains noarsenic, chromium, or any other chemical considered toxic by the EPA."If you are shopping for treated lumber nowadays, I don't think you'll find CCA-treated material in the home centers anyway since its use wasrestricted by the EPA in 2004. It will be more likely be ACQ or someother chemical.
Here's a link to the complete article - https://extension.oregonstate.edu/ask-extension/featured/raised-bed-lumber-pressure-treated-safe

https://extension.umaine.edu/gardening/2024/04/03/is-it-safe-to-use-pressure-treated-lumber-for-raised-garden-beds/

I hope this information helps you make your final decision.