I allways have known the 66/70 B and all A bodies standard manual mirror is left side because got a small angle position, but can be used on right side with small mods... milling down a little bit the base to the opposite side as far I recall.

Is that right ? or doesn't need any mod ?

or maybe got some other difference ?

on pic it looks not completelly simetric... to be mounted on either side

http://www.ebay.com/itm/Mopar-1967-1970-...855&vxp=mtr