Any set of cranks will work with your set up, as long as u get the bb also. If you use down tube shifters that does not have index, you can mix any brand of RDs, fd, cogs, wheels, cranksets.

Downtube shifters are awesome but lets face, campagnolo ergo is better hehehe

Get a pair of 600s at ebay, done. Regarding chain, a 7sp or 8 sp chain will work too.