71, I found 250 hp and 350 tq on this website. It's a PDF file.
http://www.gmheritagecenter.com/gm-h...olet-Truck.pdf
Scroll down to page 9. Your 350 is option LS9 on your SPID right?
Also your engine assy stamp might tell. It's stamped on the block on a pad just in front of the passenger side head. Get the suffix code at the end. (last 3 letters)