for an ls motor the specs are smaller than most angled feeler gauges go. Sears sells a nice straight one that covers the specs and the feelers are so thin that they bend right back to straight. For the special tool I just welded a 12 mm socket to a couple of random deep sockets and welded a bolt off the side. This way you can run a screw driver through it and hold the setting in place while you tighten the locknut. Cuts time in half using this tool. Good luck.