I have done it. It worked pretty good and was cheap enough to do..
Make sure you work with the blocks in a tub, or someplace you will be able to catch the little balls and 'needles' in the blocks.
You simply drill out the rivets holding the blocks together, cut off the stuff you don't use and then buy some 3" (maybe 3 1/4") 1/4 20 stainless bolts to bolt everything back together.
It required having an extra single block to do the 6:1
viewtopic.php?f=14&t=7964That being said... I really like this game.. So while that 'works' I think you should treat yourself to a nice set of new Harken blocks and a bit of Salsa mainsheet.. You won't regret it.