Radiator support mounting is very important to where the hood and fenders end up. Since it is no longer on the original frame, I would verify that the hood is sitting where it is supposed to be. Too low or too high will give you problems. One way to do this, when building the front sheet metal on a non-original frame, is to lay the hood, without springs and latch, in to position when the support is mounted. The gap between the rear of the hood and the cowl, should be even from side to side and on top. If you have a bigger gap on top than compared to the sides, then nose of your hood is too low and the radiator support needs to be shimmed up. After that is set, you can work on making the support lean forward or back. Then, recheck/set your gap if necessary.
You're basically building from scratch and need to dial everything in. Setting a tight gap at the cowl, will take away from some of that 3/4". Somewhere in there, I would hang some fenders and see how they line up with the hood and grill at the front and rear. See if you get good hood to fender gap. Don't be afraid to adjust hinge holes or fender mount holes as necessary to get everything sitting where you want. A round file will do wonders and won't leave any evidence that anyone can see.
