Psac,
The GMC Master Parts Books indicates that the part number of the hydrovac unit on eBay (ID model 374980, part number 2241895) is for a 370 FCS GMC.
Hydrovac ID model 374000 (part number 2208488) was used on 350 series GMCs (up to at least 1953). This most likely does not mean that the eBay unit will not work; it might work fine by swapping some of the attachment fittings.
If I am incorrect, let's hope that someone corrects this.
Roy, GMC or Chevrolet COE - what size, if GMC? Is there a part # or ID on a tag or on the hydrovac's body?
Tim
