1999 7.4l (L29) & 4L80E into a 72 K20

[CRMW]

I may end up with a 1999 motorhome (Chev cutaway) as part of a deal I'm working of for a trailer. I ran the vin and it looks like it has a 454 in it with a 4L80E. I can't register the motorhome so I was looking at parting it out. I had written off the idea as there wasn't enough value in the RV parts to justify it, but I just got thinking about the K20. It needs a tranny and engine. Its an AC cab that originally had a 350. I assume the mechanical portion of the swap will be straight forward but I'm having trouble finding out information on the electrical side of the swap. The only thing I found was the TH-100 kit from Ron Francis for $725. Does anyone have any info on converting the existing harness or finding a cheaper solution?

Chris