It might help if you try to get a little more specific with your questions so the pros on here will know exactly what you're asking. (I don't know exactly what plate you are talking about, but I know I would not be drilling on it with it installed on the engine; it may be standard to do it that way, however)
You need a water pump, so I'd pick (short/long) whichever one required the least amount of modifications for your set-up. The electric fan & horsepower gain scenario- I have no idea how that would happen. I would go with an original set up with a pulley based fan.
That eliminates one electrical variable when you get to diagnosing problems later on.
As for the throw out bearing, if it spins freely it is fine.
There should be no problem with converting to 12V engine-wise. I think 57 & 61 were already 12V, but if you already got the 61 engine running with the generator--maybe hold off on the alternator swap?. Your priority sounds like it should be the water pump for now. Good luck with it!
Brad
Last edited by ClaudeTheTruck; 03/20/2015 6:00 PM. Reason: gramma
