As many know I am rebuild my 64 old's 394. Today I installed the cam and put on my trimming chain. When I was putting everything together I had read there is a front bolt that needs to be installed to prevent the cam from "walking out" I have no idea if this motor had it before my ownership or if i misplaced it but i cant find it? is it a necessity? here is also a video for the play:

 

Is that your engine in the bottom picture ? If so I would suggest replacing the timing set with one that has a metal top sprocket. That 56 year old plastic is probably not long for the world.

Not 100% sure on the 394 but unless the engine has a roller type camshaft there is typically not anything to keep it from moving forward. The taper on the lobes combined with the oil pump drive gear keep it pulled to the back.

 

I am 100% sure that Bill is right .
Install a new timing chain and gears , and you won't have all that back and forth play .
The plastic sprocket is a no no .

 

The 63 and 64 engine have the aluminium waterpump timing chain cover housing. A cam bolt that pushes against the aluminium wouldn't last long before it wore a hole into the waterpump chamber. As stated above here you don't require one.