In most cases, reproduction parts are not duplicated. In other words if somebody decides to make a bumper guard, chances are nobody else is going to go through the trouble. What this means is that you'll get the same bumper guard whether you order through Mac's, Bird Nest, Thunderbird Headquarters, or any of the other parts houses. The only difference will be the price and efficiency of service.
I know one of the more noted makers of Ford parts is Dennis Carpenter. I don't have their catalog here, nor have I ordered directly, so I can't tell you if the direct order is cheaper/faster than ordering through one of the other dealers. I'll let you be the judge of that.