I'm pretty sure the original carraige bolts are 7/16"-20 NF threads. You can make square holes by drilling the corners with a small drill, then drilling the center and finishing with a file as seen here:

http://s176.photobucket.com/albums/w186/curt160/mods/?action=view&current=frontplateholes.jpg

See the tech tips for a template.






1952 1300 Canadian 1/2 ton restomod
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