I want to know if there is any way that I could get ahold of a duplicate build sheet for my Chevelle.
VIN# - 138678K226332

No

Build sheets weren't suppose to be in the cars in the first place, but rather trashed when the cars were done. Assembly line workers often didn't have time (or desire) to toss them so they stuffed them in the cars and left them there.

You can buy blank ones from most aftermarket Chevelle parts suppliers but you'd have to fill it in yourself AND not try to use it to document your car but could be used as a show item just like reproduction (blank) window stickers.