hi all, i'm about half done with a 1999 350 build,  i just am amazed at the changes made to this block.ok i love the one piece seal at the rear, and the roller cam is way cool.other things like the oil galley plugs at the front being changed to two different sizes still boggles me, it couldn;t save time or money,i mean in the manufacturing of the blocks. any thoughts on this?  

Don't forget the Vortec blocks deleting two of the timing cover bolt holes near the water pump.  Yes the stamped steel covers will leak unless you drill and tap the holes or switch to a cast or billet timing cover.  I also haven't been able to figure out the rhyme or reason behind some late model blocks being drilled for a roller cam spider and not using one and some blocks that have the bosses but are not drilled.  Regarding the oil galley bolt holes I don't get it either.  You can have either the old style 3 1/2 in holes, two 9/16 and one 1/2 hole or two 9/16 and one 7/16 hole.  Whatever.  

hey rev,howareya? you know my 99'vortec block has all 10 holes for the timming cover.it came with a composite cover that read replace if removed, since i'm not using the crank sensor i removed it and put a metal timming cover on. the oil galley plugs are two at .57 inches (or 9/16)and one at 15/32,the chevy dealer didn't have any so my machine shop gave me them(saved me $16 )two 9/16 and one 29/64,they worked out so far.  

Cool.  As for your timing cover, just goes to show what a wierd casting history GM has.