While you have the housing off, you'll want to clean and prep the end of the cam for the new seal. After 30+ years, most of these cam ends are all dirty and rusty, not good for sealing purposes. Buff the cam end clean and shiny with a Scotchbrite pad. This won't remove any material, just clean and smooth the shaft surface. And believe it or not, a seal lip riding in one spot on a shaft will cut a little groove in there over time. The Scotchbrite pad will take care of that too. This little tip is something you should use on any shaft that's getting a new seal.
For installing these seals, I use a vice and a couple small squares of plywood. I don't pound the seal in, I press it in from the backside of the housing, making it just barely flush with it. I set the seal and housing in a vice with a block of plywood on each side, slowly tighten the vice, and presto, perfectly installed seal. This is about the easiest seal install on this bike.