Hi guys, GT6 here! I started looking into the options wrt motors, batteries.I am just starting doing the same thing. I bought the parts from EV West. I don't have everything but the original quote was $16,769, which is in your ball park. At the moment I'm trying to connect the flywheel to the connector, but I need a bushing or something to keep the spigot bush in place. There is a good blog here of someone in Austria doing a conversion: To be continued... Montage und Gewichte
Best of luck!