Changing the timing gears is a pretty involved procedure. Always change both the crankshaft and cam gears, not just the one on the cam. You'll need to remove the harmonic balancer (pressed on) and also drop the oil pan to get to the lower two bolts that hold the timing cover on. That's a holdover from the 216's and early 235's where the main bearing clearance had to be adjusted with shims- - - -getting to those two timing cover bolts that go through the front main bearing cap was easier from the crankcase side of the timing cover. The balancer needs to be removed with a crowfoot-shaped puller- - - -don't attempt to use a 3-jaw puller and grab the outer ring of the balancer- - - -you'll destroy it.

Drop me a PM for some suggestions on how to change the cam gear- - - -it involves heating and hammering but it needs to be done correctly or you will do some damage to the camshaft and/or knock the soft plug behind the camshaft in the bellhousing area out of place and create a massive oil leak!
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!