http://cgi.ebay.com/ebaymotors/Chev...item27abc7bd2c&_trksid=p4506.c0.m245

This is a little closer to a correct accessory. I'm not saying this is it, but it might be a start to getting what you need. It's cheap enough for parts at any rate. I never have seen a foot pump in Chevy or GMC accessory guides for the early 60's trucks.
I picked up one of these on eBay a while back for installation on my '60 GMC. I'll check the p/n for you.