Standalone vs. GMPP Engine Harnesses

[lsuguy]

I searched for this so if it has already been covered I apologize.

I will be running a crate LS3 with a T56 in my 69 Camaro. I do plan to mount the engine controller/fuse panel/relays behind the dash if at all possible as I don't really want to have much wiring exposed under the hood.

Is the GMPP harness feasible for this application or am I better served going for a standalone harness from one of the vendors?

I also intend to use an AAW update main harness. Does anyone have information on how to interface these two harnesses? Which harnesses control what etc. Any diagrams would be great.

Thanks in advance!