Judging by the fact that its a '79 you'll need some sort of muffling device. If its only the rear muffler, then just weld up some pipe leading out.

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1981 300TD 4 speed manual
Euro bumpers, zender valance and skirts, H&R springs, billy HD's, leveled sls, real AMG Pentas 16x8 et11, vdo boost/egt gauges intergrated into ash tray, eurolights, led 3rd brake light