At the bottom of this page is a rundown of mechanical and hydraulic lifters in 216/235/261 stovebolt engines.
Pre '68 Dave's blog on this topic. All stovebolt truck engines used mechanical lifters. Mechanical lifers were a little more noisy than hydraulic lifters. Hydraulic lifters do not work well at sustained high RPMs, but were quieter for normal family driving.
Some people would say that hydraulic lifters are easier to adjust, and some people also say that hydraulic lifters stay properly-adjusted longer.
