Chrome pipes coming out the back of a GT doesn't look good at all unless you got an aftermarket rear ground effects kit that is made for that.
Forgive me for not answering your question, but please consider this from a fellow stanger (ultimately though, it is most important that you do what you want to do since it is your car-- just make sure that is really what you want to do).
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351W-powered 1979 Ford Mustang notchback
Stock 5.8L under custom made 4" cowl, C4 w/ shift kit
Holley 750 cfm, Edelbrock Performer RPM intake
1 5/8" MAC shorty headers, Al driveshaft
2.5" Off road H-pipe, 2-chamber Flowmasters
Front: 225/60/15, Rear: 255/60/15 Eagle GT II
Weld wheels (15x6;15x8), 8.8" Rear w/ 3.55s
14 x 4” K&N air filter.
Only a couple of weeks b4 Project FOX begins!!! 
"Red, thou art my companion. Hasten now your quickened metamorphosis to Green that I may conquer all who dare abide there beside me. May they be left thither behind burnt black." ---Fox Body