Check this site out: http://links.vintage-mustang.com/
I've used Paddock, National Depot and others. What I've found is they all charge pretty much the same price. Search this web for the closest distributor to you home -- this will save in shipping costs.
I'm in California so California Mustang Sales and Parts was my choice place to go: http://www.cal-mustang.com/
They also had the best paint that I needed.
NPD. National Parts Depot has the best prices, the best selection, and they ship out very fast. Trust me because i have dealt with so many places while restoring my car (67 also) and the other guys prices are either too high, or they wont have the parts that i need. also the staff can help out with any questions you may have.