I have 3/8" of thread engagement and the shoulder extends a little over an 1/8" into the flywheel. The end of the bolt is .220" from the front of the flywheel.

The bolt could be 3/16" longer, but I don't think the shoulder would be any longer. The counter bore in the flywheel is 1/4" deep and the the pressure plate is 1/8" thick. The shoulder on the bolt is 1/4".