Welcome to the forum Eyewonder. Sorry to hear about your truck. Here is a website that has a "guideline" of the values of trucks.
Click on the link below.
CLASSIC CHEVROLET TRUCK PRICING GUIDE Since your 1964 C10 Custom Cab/big rear window truck is in partially restored condition not sure if this would help. I have heard that the big rear window is rare, not sure about the Custom Cab portion.
This might receive more feedback if it is moved to the
Chevy Trucks Forum. This is actually the 1965-69 car forum. It will be transferred in the next 24 hours, but a copy will remain here. To go directly to the post in the Chevy Trucks Forum click on the link below.
post moved here