Ed,
I'll bet I know what fenders you bought. A guy (in Pa.) on
Maliburacing was selling a pair of NOS fenders. In fact, I see that he noted that they were sold. I think you can't go wrong with NOS sheetmetal. I've heard a few horror stories regarding the fit of aftermarket/offshore stuff.
I was fortunate to buy a pair of rust free fenders from a guy that I purchased my replacement doors from. One of my original fenders, I had to weld a patch in where it rusted out from behind my airdam. I will be using the new fenders on the car.
I could understand your concern about heat buildup under the hood...especially with the turbo. I was going to suggest SRD Art (Ben). I like what he did with his vents. They are very aggressive looking, no doubt. The GNX style vents are smaller and a little more discreet, but will they be up to the task for proper airflow?
You could PM Ben and get his consensus on airflow, etc. He drove his wagon from Utah to Georgia in the middle of summer...and it was a hot one. That was also towing a vehicle behind him, and he managed to stay under 200 degrees...190 if I'm not mistaken.
I'm certainly all for using the old fenders to practice on before cutting into the NOS ones.
Keep up the good work. It's good to see that you're carefully thinking things out.