I wouldn't buy headers until you get the heads. Or find out 100% if they will work. Ask me how I know.
The emissions legal MACs I had on the 94 would not work with the GT40p. They all bolt up to the exhaust ports, but plug angles in the GT40p is almost straight out of the head. On the MACs I had 3 or so cylinders tyhat were tight, I mean you'd probably have to remove the headers to get the plugs out. And there was one cylinder, #7 IIRC, the installed plug's electrode was actualy hitting the header tube. So I looked for some short plugs, Accell makes them, they are cheap for the SBC, but the Ford plugs were expensive and they were not the correct length for the GT40P head (yes the GT40 and E7 heads are different plugs). Anyway, I went with a set of Fox BBK shortys I also had in the garage, fit was good all around, #7 has some serious heat shielding around the plug boot. And I did get a set of MSD universal wires and made a set with 90* boots.