On those vintage machines, 90% of the leaks are at the pivot seal 060 in this diagram. they're a bit of a PITA to get out and back in. MAKE SURE TO REMOVE THE SNAP RINGS 100, 150, 080. The assembly should almost fall apart once they're all removed, or a slight tap with a rubber mallet.
There is a metal collar that often stays behind from the 060 seal on the "male' surface that inserts into the 060 seal on the axle housing. Make sure to remove that with a flat screwdriver and pry, or you'll never get the assembly back together.
Good snap ring plyers are a MUST. I got the $99 ratcheting/locking ones from Napa, they're pricy but they work well. You can buy and return or keep them for the other side that will inevitably go a few weeks/months later.