Orange 68/71/? project

[4byfour]

First time poster here. Figured I would start a thread and post pictures of the build my sons and I are doing since this board has been such a wealth of knowledge to get us started. I was told this was a 68 k20 when I went to look at it, and the frame numbers matched the title, but that's really where the 68 stops. It was clear the cab was not a 68 (headliner, cargo light, foot e-brake) but since the guy who started botching the cab floor and rockers decided to take the VIN plate off (I have the vin plate from the old original cab, just not this one)I can't say for sure what year it really is. If anyone can tell me by looking at the pics, the help is much appreciated. I know the fenders and hood they had on it were 70-72. I did pick up this 71 c10 parts truck in the deal that had a .040 over 350 in it that appears to have never run correctly after rebuild(bottom end looks good, but valve lash was awful and judging my gas varnish all over the intake had a massive vacuum/fuel leak) I have a good title for the c10 which matches door plate and the frame so nothing funny there. I am a little confused on the holes in the door jambs of this orange cab. Anyone know what those are for? Are they even correct? I haven't noticed them on anyone else's trucks so I figured the PO screwed something up there. Thanks for looking and I will try to keep this updated from time to time. Having trouble figuring out loading pictures, will have some added shortly.