here is a link to the Sm that covers the T337C. Mine is s/n 337-0775
https://agsi.sharefile.com/d-sd5e1882ac4c4e6da
I believe the fuel system for my plane is referenced on
pg 675 676
looks like the pennycap system came later?
in looking at those two pages (and maybe I am looking at the wrong pages) it talks about a unit and gives a part number for the tank unit...but it doesn't say if it is resistance or capacitance...the really fun part when you read through section 11 on fuel system, it talks about how the 337c and t337c got a different fuel gauage system and used transmitters versus senders, than years before or after....yay