I went the route of changing lifters from solid to hydraulic and the hydraulic lifters would bleed down and clack badly, tried notching the push rods, did not work, gave up and went back to a solid lifter cam and lifters and so much better and happier. Remember 261's in trucks were all solid lifter engines, unless changed out. And just for the people who do not know, you cannot mix solid lifters on hydraulic grinds and vice versa, the lobes and ramps are different.

1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration