ALL GM Diesel Diesel Engines of this thype have a blower on them, no blower and it won't run. 4-53 tells you it's a 4 clyinder with 53 cid per cylinder, so a 4-53 would be 212 cid, thus a 4-17 would be 4 clyinder with 71 cid per cylinder or 284 cid....

You can see the blower in This Picture .

1965 GMC 3500 Rescue in the Stovebolt Gallery

My Facebook Links:
Jolly Goodfellow.
the 6066 GMC Guy.
Jolly's Truck & Car Show Page.
Owner of ~ 1965 GMC 3500 Custom Rescue Squad {Black Built Bodies}.