Installing Rallye Dash in a '74 duster issues

I have a complete dash (metal frame/bezel/gauges ect....) from a '67 Barracuda. I want to set it up in my 74 Duster. I have a few hurdles.

-If I send out the rallye gauges for rebuild/re calibration will they be safe enough to use? Most concerned about water temp and oil pressure gauge. Should I worry about the ammeter? I would prefer a voltmeter. The ammeter in my dusters standard dash was destroyed due to high heat/shorted out it looks like.

-Can anyone recommend a person/company to do the cleaning/rebuilding/recalibration of factory gauges? I'm not building a show car but do want them to be accurate and reliable.

-I want to add an aftermarket mini tach into the tach delete hole. Anyone else done this?

-The barracuda dash came with a 120mph speedo. I have a 150mph speedo from a duster rally dash that I want to use. Is it a bolt in deal? What do I need to calibrate to make the 150mph speedo to work in a car that came with 120mph speedo?

-Dash wiring, I still have the standard dash/wiring harness that came in my '74. Is it easiest to just buy a '67 rally dash harness and somehow adapt it to the rest of my cars factory wiring. What needs to be done there?

-Barracuda came with a dash mounted ignition, My duster came with the column mounted ignition. (manual trans) It would be cool to have the dash mounted key but I'm sure easier to retain the column ignition and just block off the dash hole. Any thoughts?

-Any good glue/epoxy/filler for repairing those plastic bezels? where to send to re chrome plastic?

Thanks for all the help