Just did this a few days ago. I pressed the old gear off the cam, bored a hole in a piece of 1/4" plate and slotted it so it was "U" shaped. I slid this onto the cam right between the first lobe and front bearing journal. Sat the plate back in the press and hung the cam from it. I put two .003 shims (manual says .001 to .005 clearance) between the journal and the thrust plate and heated the aluminum gear in a toaster oven set at 250 F. Popped the heated gear on the crank, placed a short piece of pipe on the gear hub (but larger than the cam snout), and pressed the gear on. I had to fiddle with it a bit as it pinched the shims and I couldn't get them out; a bit of wiggling and pressing the gear back a bit got it done. I think you're gonna need a press to do it with any finesse at all and guarantee the correct clearance for the thrust plate.
