Install the gear before putting the cam into the block. There's not much of a way to secure the cam while you tap the gear on once it's in the engine. One trick we used when installing a timing gear with the cam in the block was to remove the fuel pump and have a helper hold the cam forward with a pry bar, and drive the new gear on with an air hammer. It's a lot less hazardous to do it outside the block with a press during a rebuild. Be VERY careful not to gouge the soft metal of the cam bearings with the sharp edges of the lobes while installing the cam- - - -that kills oil pressure.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!