RichieC - Take (or get the seller to take and send you pics) and post pictures of the wheels on the "1955 4100 axles" so we can try and provide better feedback on your question. A little snooping through the
GM Heritage Info Kits shows the basic dimensions/descriptions for the 4100 series wheels seems to be overall the same. There are 2 wheel sizes listed: 20 x 5.0 (standard) and 20 x 6.0 (optional) for both 1955 1st Series and 1955 2nd Series 4000 model trucks.
That being said, reading through the 1955 2nd Series
1955 Chevrolet Truck Engineering Features document (extract attached below), it shows the 1955 2nd Series 4100 wheel axle pilot diameter openings were enlarged from the previous years 4-3/4" to 5-1/4". With that in mind, I think it's important to verify if the "1955" axles are 1st Series or 2nd Series.