The lifter on the right side of your picture looks like a hydraulic lifter to me, definitely not a solid.
You could have the old lifters fixed if you wanted to work
I've had Delta Camshafts in Tacoma WA(253-572-2474) refinish several sets of old lifters that you can't buy now up scope twocents

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)