Those things just were never intended to have V8s. I've had three; two 68s and a 69. One of the 68s with a 'vette 327 in it. With the straight 6, they are perfect. But with a V8...
Yikes! The hotness!
With a little judicious bending here and there, the belly pan can be made to scoop a lot more air and divert it up toward the radiator. It does help.
But then...so does driving with the hood open...
Also, when dumping the clutch to show off that V8 speediness, the most likely thing to go wrong, is that the input shaft on the pinion gear will snap and the driveshaft will first hit the ground before coming to rest sticking up through the brand new hole in the floor.
Don't ask how I know that.
Seems like your shakedown cruise is going well. Should have the bugs worked out about the time you get home.