If you can get to the Milwaukee boat show this week or weekend, I believe their are people there showing their classic boats. Likely some of them would have good networking connections to help you find what you need. You likely can see some cool boats and also get many questions answered regarding anything classic boats. Just a thought. Likely those AOMCI people have answers and might even have spares of what you need.
Not a problem. If you shop around and find two sets of simplex/Evinrude/Johnson two handle controls they can be married together. They are designed to be piggybacked. All you would need are longer stainless bolts to hold them together. A simple bolt up job.