Old thread Revival!!
Just thought I'd mention that with a very small amount of grinding, I have fitted the OEM pegs off my 2012 YZ450 to my 1990 YZ490.
These OEM pegs also fit:
2007-2015 YZ 125-250cc
2008 - 2014 YZF/WRF 250-450cc
So if you can find a second hand set of these, you can make them fit.