What are your plans for the car? The stock exhaust tips look nice but if I was building a modified car I'd go a different route. I think some 2 1/2" or maybe 3" turndowns, angle cut so they are horizontal to the ground would look great. Only have them hanging down maybe 1/2" from the bottom of the valance.
If your going with stock type wheels I'd go with the cut-outs. If you are going with wide tires in the rear... removing the 74 bumper guards and going to have some serious HP, I think the turn downs would look better IMO. I don't think you can go wrong either way.