Replacing Ticking Hydraulic Lifters

I've had great luck with a mixture of half ATF and half Marvel Mystery oil freeing up what you're describing. On one small block I was able to use a drinking straw to feed some down to each lifter by squeezing it between the pushrod and pushrod hole in the head. A few light taps on top of the rocker arm with a wrench or small hammer and then let sit for 10-15 minutes. May be worth trying, before a teardown and clean.