Getting back to the OP's question, I would prefer LX style tailpipes angled lower than the stock bumper over notching or drilling a hole in the bumper cover. To get the required angle, pipes can be cut and rewelded to make them work.
Those of us that have been foxbody guys for 30 years+ have seen it all when it comes to this topic.
Some notes:
A Saleen rear bumper does not look right on a gt. The side skirts are different.
Cutting holes in a gt rear bumper is a great way to force yourself to buy a cobra valence.
Gt tail pipes look all sorts of wrong on an lx.
Angling straight pipes down to go under the bumper does not look natural.
The cervinis rear bumper doesn't say cobra on it, so it's probably the way to go. Though if you are getting paint work, may want to do the wing too at the same time.
One of the trends back in the 90s was 3in pipes through gt bumpers. I can only imagine how many rear bumpers were ruined by my friends.
I think LX pipes look the best on LX cars or GT's with the rear Cobra bumper. I hate pipes on GT's that point down or angle down. At the end of the day it's your car so whatever you like just please do not cut holes in the bumper like previous members said. That is the worst looking thing ever!
BAck in my day most performance exhausts looked like my old Dodge did
Having " pea shooters" sticking out the back looked like sh!t...
While it was a mistaken order on my part getting the GT pipes for my LX, I am not quite ready to order another new set of cat backs yet
I might try to cut part of the angle part off to make the amount of pipe shown less.....