vhaines, only if someone swapped a 24 motor into that '97 truck, or it's a 98. 5 like jgillot says.
Have him look at the engine tag on the timing cover at the front of the engine. It will have a build date in 05-22-98 format for example. Then look at the door sticker, it will say "Date of Manufacture" giving month and year the truck was built. If the engine is original the build dates should be within about 4 weeks of each other, the engine always being older of course.
Vaughn