Cam Timing 340

Trusting the marks on the gears is such a crap shoot. I'd strongly suggest degreeing it in so you know for sure.
But if not...........
Take the chain off , rotate crankshaft until #1 is at TDC ......the mark on the crank gear should be at 12:00 , but verify this by noting the position of the piston. Easy with the heads off , not too difficult with them on. Just put a screw driver in the spark plug hole and SLOWLY move the crank back and forth until you are certain that the piston is as high in the bore as it is gonna get.
Take a couple tries , and make sure the screw driver isn't binding anywhere while you do this.
Then put the gear on the cam and locate the dot at 6:00.
Remove cam gear , install chain and hope the manufacturers of your timing set were very good the day they made yours.