Much thanks for all the responses.
I am up and flying now in P3D v 4.5. I have added about a dozen freeware aircraft thus far, doing a lot of panel.cfg editing (adding new gauges, moving gauges, etc.). Most is working well, but I have a few issues:
1. Generally, some gauges from FSX work well in P3D v 4.5 and some do not. I presume this is the 32-bit vs 64-bit issue. This just becomes a trial and error thing as I try various gauges.
2. Because my GoFlight modules continue to be unreliable in P3D, I load a particular AutoPilot and Radio Stack in each aircraft. I use the files for these 2 gauges from FSX (which I installed in 250+ planes in FSX). I have been installing these in all my P3D planes (all freeware aircraft). In a few of the planes (WW2-type), these instruments do not seem to power up or function. Are there specific settings in the Aircraft.config file, under [electrical], that I have to change (or have present). Also, the GPS in one of these planes does not light up either so I am wondering what kind of issue this is.
Final comment - as a real-world pilot, and having 75,000 hrs logged on FSX over the past 10 years, I am not that "dazzled" with P3D thus far. Many interesting features (which I will likely never use), but I do not see great differences in the day-to-day things I do with a flight simulator, so we will see. I am keeping an open mind, since I spent $200 for this simulator.