Well, I am not saying the timing cannot move. I simply cannot see how. Especially on this. When the block is cleaned up, I'll post better pictures, but the idler gears are trapped by the block casting, plus it's just a very tight fit between the idlers and cam and crank gears. You have to ge them "just perfect" before they will even think about dropping in.
Even still, it would take very little movement to make up for a few degrees of timing. It's still early in the game. I may still attach one of the idlers to the front of the block and make it a fix idler system. Either way, it will have gear drive.