It's been a while since I posted, but I have to since i learned this lesson the hard way a while back.
I'm glad to hear that you have the right cam, because that commonly the first mistake. Now youe lifters will ride in the right place in the bosses and not come up too high. Now you just have to drill and tap the valley of the block (after grinding out those "XXX"s and yes, you should clear the top of the bosses so that they don't wear on the dogbones.
You can get away with not clearing the dogbones as they simple rattle around with a lot of play, but I wouldn't leave it that way. Better to clear them so they're not causes little metal shavings to rub off when they're rattling against the outer cylender walls there.
There you have it, the spider, dogbones, lifers, RBC cam, and machine work.
ID89GT: its better to find a 94 or later block and run the HO style lifters. That 90 block isn't any better than a 94 or later, so why limit you cam selection when you don't have to? The 74 and earlier blocks are pretty much the only ones worth doing that to (converting with the HO setup) ALTHOUGH, running linked bar lifters is another option for using your existing 90 block, or any non roller for that matter (but cost $500+ a set new, about 300 used).
