I have a set of Hooker SuperComps longtubes that are 1.75" primaries on my stroked Windsor in a 65 Mustang. Did you look them up? The only drawback is that the collectors hang too low and really hurt driveability on the street, but then again, my car is lowered almost 3 inches. I am taking them off and selling them.
You can also try
www.fordpowertrain.com , ask for Stan. They have the closest to custom made you can find.
Here is another one highly recommended. They have what you are looking for.
http://www.accufabracing.com/exhaust.htm and ask for George.