I intend on using a Permacap from Kleen Wheels. The only issue is that the Permacap is compatible with only screw type filler necks. Fairly inexpensive at 15.25 plus shipping. Ordered one this week, waiting for delivery.
Here is the link.
https://www.kleenwheels.com/vmchk/Pe...rmacap-PC24001
I have a 1970 SWB and am using the filler neck, etc. from a 96 S10 to fill through the side marker.