Hey Darkfire, that notch locates the sleeve in the block, if you look closely you will see a small pin in the notch. I have seen some of the head screws not tapped deep enough to get a good seal, but they were close. I have chased the threads in the block, out with a blind hole tap, to clean them up make them just tad bit deeper. If you dont have a tap then grinding the tip of screw down just a bit will help just be sure to clean the threads by grinding a bevel on the end of the screw. Dont grind too much, take your time. Now, your head shims,, if they are flat and not kinked they are fine and they should last the lifetime of the engine, you DONT need to replace them!!

Exhaust gaskets will tear often if they are installed improperly, when you slip the gasket over the block flange be sure to get the ridge on the inside of the gasket into the groove on the block flange. Then lube the outside of the gasket and the iside of the header pipe with light machine oil. this will allow the header pipe to slip over the silicone gasket easier and wont "grab" it. Then be sure to push the header on squarely and seat it completely!!!

hope that helps!!

If you have any further questions feel free to ask, bro..