[Bill Harris]

With the D1AE-GA heads you can only run it as a '71 351/285 factored at 324 for GT or 351/330 (the Boss 351 engine) factored at 340 for GT. The Boss engine can only be run with a stick. The Boss engine could have some advantages if it were running in stock, although I can't recall if anyone that has done it. In S/S the advantages are less since you are not restricted in cam/valvetrain or intake manifold so the only thing you lose is a little compression, almost certainly not worth the 16 HP factor difference . You can use the 780 Holley/Quickfuel carb on either.

The code on the block is irrelevant. If it is a Cleveland block, its good to go.

If you go with the 351/285/324 these are the classes you can run (assuming by "Coupe" you are talking about a notch, not a fastback body).

Click on the pix to make it larger/readable. GT/DA to GT/FA are likely your best bet depending on how much weight you can get out of it. 3078 lbs without driver is pretty light for a '69 Mustang.