That one is hard to find believe it is a one year only Roadrunner? The third pin is for a warning light, most have two and the dimple also is rare. I love this stuff.
If it has a real transistor on a heat sink instead of buried in the potting. We beat the hell out of it here
https://www.forabodiesonly.com/mopar/threads/1974-brain-box-saves-the-day.472657/
No way like the old boxes, it has a fake transistor on it and a high fail rate. read this. Bit long but we really hit all the issues.
https://www.forabodiesonly.com/mopar/threads/1974-brain-box-saves-the-day.472657/