chevy042,
Welcome to Stovebolt.
A quick look at your pictures shows the wiper shaft
might (?) not be original to your '41 truck. They should have a whole that passes through the shaft where the original style arms connect and get retained (see picture below). Check out the pictures that are part of the vendor ad for
1939-46 Truck Wiper Arm details. The 4th picture shows a detailed breakdown of how the arm gets mounted to the shaft, which may help you out.
If it turns out that yours aren't correct, you will need to try and locate replacements to get your wipers back to what the were originally.
Am sure others will be along to add more info and details.
Dan
