I already told you what I would do. I would sell the 75's and spend the money on the DOOE's, or buy a set of after markets.
But with that said I can't tell you what to do, it depends what your looking to accomplish. If you dont want to spend alot, are not concered with ultimate performance and already have a set of ready to go 75's by all means use them since you already have a 12 bolt intake to use with them. Just plug the thermoactor holes and your good to go. It will run fine, it just won't have the power the DOOE's would make.
As for the 302's forget them, In my opinion they were barely sufficent for a 302 let alone a 351 and with all the drilling involved it isnt worth it. mm