Hi,
as I promised, here is my conversion from the old GMC T/S switch to a 64-66 Chevy T/S signal switch.
Maybe it will help someone who doesn't get an original GMC turn signal switch anymore. The new turn signal switch I bought on eBay is a STANDARD MOTOR PRODUCTS TW14.
You can reuse the following parts: cover for the steering column, the shifter housing with the shift lever, steering column and the turn signal lever. The only part that is needed new for the Chevy T/S switch is the turn signal housing. This housing fits directly on the steering colum with the bayonet lock. I was lucky someone stopped his Chevy C10 project and sold it in pieces in the local ads
The colors of the wires of the new T/S switch are the same like on the old GMC T/S switch. I connected it with the original wiring harness from the truck. Everything works fine!
Please see the photos:
1. T/S switch housing GMC and Chevy. Left side Chevy, right side GMC.
2. New Chevy T/S switch in the Chevy housing.
3. Chevy housing mounted on the steering column.