See if you can borrow a mates cigarette lighter from another 70s model with a similar lighter size. Newer cars have more compact ones.

I used a 12V hot water jug in my 1200 cig lighter once, I used to run a higher ampage fuse, and I almost set fire to the dash

Certainly sounds fishy If the cig lighter fuse is blowing.. you are connecting to the right wires.