273 valve stem seal replacement

I’m thinking about replacing the valve stem seals on my 65 235hp Dart GT convertible It’s been many years since I’ve done this with the heads still on the car, and I’ve never done it on a 273 Mopar. I was planning to just pull the rocker arms and pressurize each cylinder with air. There used to be some tools for Chevy’s, etc. for this that would compress the spring so you could pull the keepers.. I don’t know if there is anything for the little Mopars. Does anyone have any advice/suggestions for me on this? I seem to remember some tools that hooked under the rocker arm shaft that let you leave it in place, but not sure. The engine still runs pretty good, just smokes a little the first time you get on it after it’s been sitting. Compression is pretty decent all around, and I think the valves are all still ok. I don’t want to pull the heads yet if I don’t have to. Thanks.