With over 100K and more than a 1/3 of century, you're overdue for a new timing set. (and while you're there,convert over to a neoprene seal, so my free oil flow mods, etc, etc, etc... You know, the ''as long as I'm theres'', and the ''might as well while I've got it torn down this fars'')
Odds are your valve springs are much and that's why you feel about 100hp down (because you are).
If they're the stock springs, you DEFINITELY are leaving a bunch of power on the table. (and burning exhaust valves/seats doing it)
Odds are your small vacuum lines are shot. If you touch them and your finger comes back black, they're long since gone. Make sure your check valves are check valving too.
You didn't list any other mods/updates/preventative maintence, so I can speculate on any thing else.
