Yes I made them custom.
I was very simple to cut them out of 1/8" plastic.
For the rear I was able to use existing fasteners and only had to bend up a pair of small brackets for the bottom connection, again to an existing bolt hole.
For the front, they fit tight between the fender liner and the wheel flare with only a single bolt holding it to the wheel well, again using an existing hole, so no need to do any drilling.
Used a strip of stainless along the bottom and bolted a rubber extension to each flap. They look very good.
I have done the same for my Firebird.
They are all 12" wide and very close to the ground so from the rear, it looks like very wide tires, and do a very good job of preventing any debris from hitting the body.