http://gmupfitter.com/files/media/photo/623/New_Elect_BP_05_27_15.pdf

"The scope of this Electrical Manual is to define General Motors recommendations for the design and installation of non-OEM (Original Equipment Manufacturer) low-voltage electrical systems and components in GM vehicles by personnel engaged in the conversion of automotive vehicles. Also included in this manual are guidelines for the interfacing of Upfitter installed electrical systems to the General Motors OEM electrical system. This is not a "how to" manual. It assumes the reader has technical expertise in the area. Ultimate responsibility for all work rests with the Upfitters."

Lots of free, useful information here, including wire gauge and ampacity charts, terminal and connector recommendations, and guidelines.

P. 49 covers crimp-and-seal splices. The part numbers for the recommended crimp plier tool are:

GM: 12085115

Kent-Moore: J-38125-8

Tyco Electronics: AD-1522-1 Crimp Tool (047011-000)

Note that GM now recommends TXL wire in wiring repairs:

http://sandyblogs.com/techlink/?p=1375

GM part numbers for TXL wire can be found here:

http://sandyblogs.com/techlink/?p=1418

Michael from Alabama