I agree, the elevation difference should have no effect, PO noted new plugs and carb rebuild. I would pull the carb apart and inspect the spring loaded power valve, if it is stuck in the "UP" power position the main jets are flowing maximum fuel. Also double check the float level. I have had 180 degree t-stats that run too cold, might want to go back to the 195 for a test as the warmer engine will help with the rich a/f ratio.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy