I took a Model 70 Bell and Carlson Win. Extreme Weather stock (w. Aluminum bedding block) and tweaked the inletting for a MRC 1999. Like Utah alluded to, the main thing is notching out space for the side bolt release and maybe a teeny bit around the tang area. But it is nothing a little patience, steady hand and a dremmel tool can't do.
McMillan will also ship you a drop in stock for your action. If you did want to save a bit of $ and are not too concerned about weight, the Bell and Carlson M70 Medalists w/ bedding block come in around 29oz and would be your huckleberry.
http://www.stockysstocks.com/servlet/the-459/Bell-and-Carlson-Browning/Detail
