for anyone who is interested www.subysolutions.com is having a sale on gp moto top mounts. regularly $799, they are on sale for $499. the core dimensions are 20.125" x 7.625" x 4.5" and the core is gunmetal black. they also come with a cast y-pipe and the factory bypass valve mount is retained.
the sale price is in this months snail mail catalog. it is a close out item. call them and ask for the close out price (1-888-773-1212)