Dooley's chart is excellent, and you can see the distinction between the "old" (R/V) style truck and the "new" (GMT400) truck based on the line drawings.
You can see the regular cab dually pickup, as well as the regular cab chassis and crew cab chassis variants in the old body style.
I did pull the GM Heritage Center info packet for 1988 and it was, unfortunately, not very clear and very GMT400 intensive. It did, however, show a carbureted 454 engine in the Powertrain chart.
http://www.gmheritagecenter.com/gm-h...olet-Truck.pdf (page 53 - 55 of the pdf)
K