[QUOTE=POWERSTROKE;69517]Whether it was a lowly little LoadStar with a 345 cid V-8, or a FleetStar with 478 V8, or a C65 with 366 V-8, or C70 with 427, anywhere from early/mid 1960's to late 1970's, they all had true dual exhausts.
Powerstroke, you failed to mention the bigger GMC truck Powered by the bigger displacement V6 engines that also came equipped with dual exhaust?
late 60's up to 1974 on H & J Series 7500-8500 trucks equipped with 401M. 432,& 478M engines. Also the 73-74 C6500 series equipped with 379 and 432 engines, the same should apply for T series tilt cabs of that era.