Hahaha....sorry that last pic made me laugh...i wasn't expecting a HUGE plug......
So, I like what you have going on now with the gauge pod......what's the next step? Not sure what to do, or just need to get it done.....looks to me like you're on the right path.
Plastic weld to secure the plastic to plastic, then duraglass, then filler then paint and you'll be good.
What are you going to do about the warning 'section' that the gauge is blocking? Possibly cut out a hole that you can look through to view them still??? Looks like your gauge will clear it.
If you have a smart phone, you can get a Bluetooth ODBII sensor plug for it