The Stovebolt Site Forums The Parking Lot Panels 'N Burbs Burb body mounts

Here is a photo album showing 1954 Chevrolet Panel truck 1/2 ton mounting points with original blocks.
Panels 'N Burbs mounts are pretty much the same.

Maybe these guys can give you some insight. CPI TRUCK OR Dreamers Hot Rods -- Enlarged Photo
They have the below.
BED AND CAB TO FRAME MOUNT RUBBER BLOCK SET CHEVROLET GMC TRUCK 1947 - 1953
or
polyurethane square bar
You could cut it to what ever length you need.
But I would still use the rubber vibration Isolator Pads. Body Mount Pads - Panel, Suburban
HERE are some Universal Polyurethane Pads/Blocks