FWIW, the potting material in some ECUs can deteriorate over time and leach out on their own. Opens the possibility of shorting out.
Here's one I had in a box for a long time and what it looked like several years ago after I "unstuck" from the cardboard...........
View attachment 1716275880
For kicks I put it in a plastic bag. What it looks like today..........
View attachment 1716275883
MyMopar has a '73 Dodge FSM free to download which may be useful if you don't have one.
[URL]https://mymopar.com/service-manuals/[/URL]