Just a couple things........I'd pop the oil filler cap and watch for some huffing and puffing....might be more crankcase pressure than your draft tube can handle. It could/would indicate worn rings or valve guides and new seals wouldn't do much good. If you don't have excessive blowby, it would be time to go after the seals. Unfortunately, the fixes for the rear main seal and the timing cover seal are not something you crank out in a couple hours.
Yes, the radiator does need to come out to pull the balancer, the repair sleeve recommended by Tim is a lifesaver. I've always pulled the timing cover, replaced the gasket and seal and seated the H/B with the cover loose. This insures that the new seal will center on the improved sleeve on the balancer. The down side of this, is that to get the timing cover off, you'll have to drop the pan to get the 2 bottom timing cover bolts that are installed from the inside. While I'm in there, I like to drop the front main cap, tap it with 3/8 threads, drill out the (2) 5/16" bottom timing cover bolt holes so I can install the bolts from the front. With the pan off, you can wrestle with the rope seal. That is in itself, is another whole kettle of fish!!!
If by chance, you have excessive blowby, you may need to take a closer look at the compression and oil pressure and the general overall condition of the engine. Nobody welcomes the need for a rebuild but replacing the seals on an engine with questionable oil pressure, excessive blowby and leaks might just be putting a band-aide on a more serious problem. Hopefully, you can avoid that situation but you've got the winter months to get things squared away. I hope this helps.
Dave
