68 Dealer Installed Saddle Tanks: No Sending Units?

[crakarjax]

I'm guessing it was different for various dealers, but after trying to figure out where the switch was in my truck to user the 3 tanks' senders, I realized that the saddle tanks had no wires coming from them. I haven't pulled the tanks out but it seems like they just don't have sending units installed.

Was it customary back then to run the saddle tanks dry, relying on the cab tank's gauge when you get to it? I was told that running an engine out of gas was not good for it, but maybe that was only relevant to EFI setups.

BTW this truck originated in california.