5.2 5.9 magnum EFI plug and play harnesses

This thread got me to thinking; if I were to swap out the very worn out 360 in my 90 W250 for a Magnum, how much of a pain is getting rid of the TBI wiring and installing the Magnum harness? The truck is not worth the grief of a monumental rewire and ripping into the dash, but if it were a simple plug and play, I might be game. Getting this modified harness save enough of the conversion PITA to be worth while?