GMC did you no favors. Below is the list of GMC exhaust pipes from 55.2 (Y series), 56 (X series), 57 (T series), 58-59 (S series V8 engine serial number below 336-35000 [engine based on 58 Pontiac 370] and above 335-35001 [based on 59 Pontiac 389]). I'm assuming the "front" pipe is the Y pipe from both manifolds to the front of the muffler. Mine had been "dualed out" before I bought it in 1990.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
