I was going to do the 240 high ports but after conferring with big bore Ford small block guru Duane Busch he said that the 7721 Edelbrock Victor race head would work much better to reach my 93 octane pump gas NA 9 second goal. He said that the 240 high ports would have left a lot of HP on the table and it may not get my heavy street/street turd there.
New 7721 castings were hand ported, flowed, and assembled by DB with stainless steel valves were cheaper than a pair of highports from TEA. Definitely a lot cheaper than major porting places on the net advertise.
Mine were ported for my NA needs with 381cfm int/271 cfm ex @ 7000 rpm. Intake and exhaust ports are both raised on the 7721 head--.380" intake and .520" exhaust. My heads are far from maxed out and can further ported with larger than the 2.150" intake valves that I have. Ports can be made huge if needed. This is a head that can grow with your needs.
The 7721 uses any standard Edelbrock intake (which should be flowed to the heads.) I use the 2924 Super Vic but a 2828 is more performance oriented. 7721's should be run with shaft rockers so that is an additional expense--but necessary for higher RPM's. Also they use an oddball 2.5" header flange. Not hard to find but not that common either.
The best thing about using DB is that he not only did he do the heads, he had a hand in spec'ing the cam, compression, carb and exhaust size. Even the rear gear. He still checks in on me and suggests changes I can do to my car. Although I have been slow to follow through with all of his suggestions, I ran a 10.004 just last week in the heat/humidity with my small tire car.
The only place that I could find off the shelf big tube headers that were larger than 1 3/4" for a Windsor in a stock suspension Mustang was Accufab. (Remember that I installed the 68' shock towers/suspension in my car a couple of years ago.) Accufab offers both 1 7/8" and 2" headers with a choice of flanges and collector sizes. Both diameter headers are semi-designed to sort of fit the 67+ engine compartments but definitely expect that you will need to reroute some tubes to get them to fit with out interference with the towers. I bought the 1 7/8" tubes with 3.5" collectors as that was what was spec'ed by DB. Notching the 68' towers probably wouldn't have been needed but I went that way for more access to the plugs and things--as far as tube rerouting there isn't much to gain at the towers since the exhaust flanges are almost at the LCA bolting location. I am still not 100$ atisfied with the Accufab headers and plan on rerouting some tubes to raise the collectors higher over the winter. They are OK height for a drag car but not for my street/strip car.
My suggestion is to figure out how you want the front suspension to be and go that route with the motor/headers from the get go. Doing things twice leads to added expense. Band aids won't be cheap and neither will replacement part if they are already on the verge of being marginal. Thanks to the Fox body platform, there are lots of bit tube headers for R&P cars so that might be your best route BUT as you probably have noticed, its an expensive route to take. What you have can be made to work with minimal expense (except for the headers.)
There is an internet forum poster named jasonn (yes 2 n's) who runs a stock type front suspension 70' mustang with a mild 427w motor (10.81 compression), 240 high ports, big FTI SR cam, 2924 intake, 2" tube Accufab headers, and he recently ran email@example.com with a 350 shot. Perhaps you might hunt him down to pic his brain.