My newly acquired 72 454 4 speed came with factory side exhaust installed. The rear exhaust cut outs are still there so I do not believe the side exhaust are original to the car. What do you guys suggest? Keeping the side exhaust and plugging the rear exhaust cutouts or removing the side exhaust and installing the original exhaust setup?

Side pipes were not available in '72, so they are not original to the car. Keep or not? Up to you. Personally, I would keep them and get the proper rear valance, or modify the original to eliminate the exhaust cut-outs in it. 

I agree w/ Adams' Apple.  Probably not impartial since I have side exhaust on my '73.  I always wondered why it was a one year option because I thought it was a very cool design.  They are very expensive to add now which is why I had mine Jet Hot coated.  Had to have the covers replated since it was my daily driver and the Midwest winter salt literally ate them up.  😧

Thanks for the advice guys! I will start pricing the rear filler panel. Any tips will be much appreciated!