Unhappy 360 (At idle)

Flaps open full time will work. It's a nice feature when they are functioning but not that important for what you want to resolve.

EGR block off plate I don't know whether that is enough or not. If it is great. There are a number of ways the EGR passages were routed. I don't know them that well and not your 360 at all.

The EGR Valve was a simple vacuum-operated device mounted on the drivers side of the intake manifold:
EGR Valve.jpg
Manifold.jpg