Here's pictures of my overbuilt cab cart, It was built from 4X4's, 2X4's and metal deck connectors, the Wheels are 4" from Harbor Freight (On sale) a buddie of mine has 2" on his and was amazed how easy mine rolled compared to his.
http://www.chevygmcofkc.org/Gallery/data/3002/1DCP_1306-med.JPG
http://www.chevygmcofkc.org/Gallery/data/3002/1DCP_1305-med.JPG
I overbuilt it because my cab has been extended so It's a little heavier than normal. Also I wanted to be able to transport it to my sheetmetal and body guys on a trailer safely.
http://www.chevygmcofkc.org/Gallery/data/3002/1DCP_1348s.jpg
Mongo


Mongo's Garage
Vintage GM Truck's & Parts
https://mongosgarage.com