You likely won;t find much, if any direct applications listed for a full size Ford. I have Flowtech 12100's in my car, but the collectors had to modified slightly to better align with trans crossmember. Shorties will leave all the custom fab to the piping to get up to the collector. A good fabricator should be able to tell you if a set of headers will fit reasonably well by looking at pictures and seeing your engine bay, but don't expect any set of generic, or specific headers to drop-in without some tweaking. FPA seems to have lots of options, and some that may work for your application. They are a premium product, for a premium price, but they will speak with you and give you some advice and recommendations.
I've called a few but they dont really know. Its such a rare car that not many know it too well.
I'm going to try the flowtech tri-y headers. It looks like it'll clear the steering knuckle. I'll let everyone know.
I had a 70 galaxie 351w. Never found a pair that fit. Long tubes or shorties.
My advice. Get k code knock off manifolds for a 289 mustang. They will fit no problem. More durable. Won't leak as easily and flow plenty well for a mild street machine.