The only thing in the back of the cam is the rear cam plug and the cam does not ride on that at all. The rear thrust face is the front of the block. Stock, there is no forward thrust control. The lifter contact points (and I think the oil pump mesh direction) are what keep the sprocket back against the front of the block.
Here ya go with the info:
www.slantsix.org/forum/viewtopic.php?t=24119&highlight=