Thanks for the input, Ed. BTW I worked at Longmont Hospital in the early 1990's until I moved back east. Great area.

http://www.oldgmctrucks.com/Photos/GMC_Numbers.htm

According to this chart, my engine is indeed a 228 (see "Head Casting Numbers column, #6107412).

The 302 sounds intriguing, I read about the more sofisticated military version GMC made, is that ever found nowadays?

Brad