Nice score. I bought a 71 K10 stepside last year, with probably the same six banger in her. Mine was so rotted that I ended up giving up on it and selling it. At a loss
. I think the six cylinders were either 250 or 265 inches roughly. Not bad engines, but why not dump a 350 in there? Or did you say "RESTORING". Personally, I wanted a 454, dana 60 front and 14 bolt FF rear, and 38s or something crazy like that. That's why it never got off the ground. I have most of that hardware in my 87 K20 now, plow yard/horse around truck. Good luck!