RE: Gas Type Engine Radio Interference
There is no problem using metal push rods as long as it is isolated from the engine with a plastic link and is not allowed to make contact with the engine in any way.
Just keep all of the ignition components as far as you can from the radio equipment within the confines of your airplane.
Make sure you use a resistor spark plug if you can. If not you will have to have a shielded ignition system. If you don't have a shielded or suppressed ignition system putting the radio in the tail and using a plastic throttle push rod won't helo you.