Hey guys. Working on a 396 I pulled out of my chevelle to drop in the 73 K5 (bought a RJ502 for the velle). Just pulled the timing cover and discovered the chain is worn to the point I need to replace it before dropping it in the truck. So Im considering a gear-drive. The problem is Ive never installed one, and when looking into them, its said that "some machining may be required" to install them. Im guessing this is a clearance issue with the block? Is it a minor mod, like a dremel project, or is it more serious? Im not gonna tear the whole motor down to do some major block work, I'd just go with another chain set if that's the case. Anyone installed a gear-drive on their bigblock? Any info/opinions would be appreciated. TIA guys.