I just installed a Lokar dipstick. It says to be sure you have the lower dipstick tube installed GM Part#3951600. How can I tell if this part is installed? I know it slides into the block and has a flange that keeps it from dropping into the block. The new dipstick housing was a good firm tight fit when I put it in and I assume it would be a loose fit without it.....I can't see by just looking at it. Also, If I did need to install the tube would I need to remove the header? Thanks!