Is there any way to decode the build sheet other than figuring out the option codes? In other words, the codes for boxes 11 thru 106 on the build sheet itself. Thanks.

I can help a little...most of the boxed codes are pretty self explanatory, some are simply codes to identify the parts by the assembly number, such as pullies, I P harness, console harness, body lamp harness, etc.

Some that are easy to identify, aside from the obvious model. The following is from KC cars:
Box 11 ~ Frame: XU-R for sport coupe, XX-R for El Camino & XV-R for convertible.
Boxes 13/14 ~ Front/Rear Springs: example GB for a front spring is part #3960665 with a cutoff length of 125.89, wire dia. of 659, total coils of 9.22, deflection rate of 435 lbs per inch, 15.52" free height and 11.7" @ 1650lbs working height. I got this info from the GM restoration kit. Examining numerous examples shows what springs were installed with what other types of options. This happens to be the spring for the F41 in a L34 396 sport coupe. The same F41 option in a LS5 454 sport coupe got springs coded GC which differ only in cutoff length (125.94), 15.32" free height and working height at 11.7" @ 1780 lbs. The F41 suspension was not a single, all-inclusive set of springs, shocks, etc. but tailored for the specific engine/body/etc.

Instead of going box by box, check here (http://www.chevellestuff.com/tech/70_build_sheet_kansas.htm) for some KC build sheets. It's a table of the boxes and specific codes for three cars; one a L34 396 w/F41, P/S, 4-spd, one for a L78 El Camino w/F41, no P/S, 4-spd, and one for a LS5 w/F41, no P/S, TH400 - all have the optional gauge package.

A few items of interest to note are the different tach codes (72), speedo cables (73), speedo gears (92), starters (32), etc.

I have other assembly plant code sheets, Atlanta, Arlington, and Baltimore and not all the build sheets I have are listed on the code sheets but there's a good representation.