I have to correct myself, it's TCS (Transmission Controlled Spark) instead of TSC. I was close...lol... Anyway, it's been tough to find info on that system. All I know at this point is that it kept the distributor from advancing until the tranny was in high gear and the engine was warmed up. It reduced emissions very slightly but also increased fuel consumption considerably. I have yet to see any pics of the system completely hooked up, or even a diagram for that matter.
I do wonder, though, if one of those relays is an anti-dieseling relay. I have seen a single pic of that and it looks similar to the one on the left side, like a horn relay. It's tough to tell what this truck was originally equiped with since the original carb is gone. I did think it was the horn relay as well, until I found that the horn relay is in the cab. I'm doing a lot of learning with this '71.
