There were kits for these going way back IIRC even J.C Whitney carried them. Shipping would be expensive but fitting a later model kit should not be a problem. But... one of the problems, especially with the homemade conversions, was the bed and cab alignment. All too often the bed sat higher due to a subframe for the bed. Plus the bumper needs to be addressed for clearance or mounted to the bed/subframe.
Here is a thread link and two of the auction pages for some reason I cannot write and save the pictures, probably my ISP again. If someone would post the relavant pictures it would help for the archives later.
http://67-72chevytrucks.com/vboard/s...d.php?t=554699
http://cgi.ebay.com/ebaymotors/1970-...item2325dc82fc
http://cgi.ebay.com/ebaymotors/ws/eB...m=150963211596