So the question regarding hydraulics and a powerglide block are relevant to 1950 through 1955 blocks. Powerglide blocks cam with hydraulic lifters. You can retrofit solids or use hydraulic lifters, along with the appropriate cam. Stick shift blocks were solid lifter only and were not drilled for hydraulics so you can only run solid lifters. In 1956, GM made a few changes including the elimination of the two separate block thing. No shims, neoprene seal, 848 head for example. So from 56 onward, all passenger car blocks came with hydraulic lifters regardless of whether those motors used a standard transmission or automatic transmission. As for hydraulic lifters, 55-58 use a GM lifter that is slightly different the the 59-62 hydraulic lifter. So two different part numbers, valving mostly. In 59, GM made the last of the changes to the oiling system of the 235 and apparently specified some differ5e3nt valving. Aftermarket generally lists one part number for 56-62 hydraulic lifters.
NOS 55-58 GM lifters are an unbelievable bear to come across. 59 and up NOS GM hydraulic lifters are just a tiny bit better, but still a bear to find. These are the very best lifters to use. As for aftermarket, Sealed power, TRW, McQuay Norris, Johnson, Elgin, all good brands so long as you can find them as made in the USA. These are also now a real challenge to find. For whatever reason, the new manufacture lifters, and new being relative as this issue has been going on for like the last 30 years now, have not had a very good reputation for longevity. It is common for these lifters to fail and collapse shortly after you start using them.
So with the cost of machine work and parts these days, I think I would be very hesitant to used a new hydraulic lifter if I was unable to find NOS or RNOS USA made hydraulic lifters. New solid lifters on the other hand, while not as quiet as hydraulic lifters, seem to be a lot more durable and less in the way of issues re brake in and running failures. Do they need to be adjusted once in a while, yes they do but not as often as some would make you think. That and HRL is right, its a cup of coffee and an enjoyable hour in the garage tinkering with the motor a bit. Once you learn how to do it, its no big deal.
Now the other possibility, Rocker Arms Unlimited in California is really the only place to have a set of rockers rebuilt. One of the other services they offer is lifter resurfacing. If you have some used lifters that are not worn or scarred up beyond their serviceable life, you might be able to tke them apart, clean them up, send them out for a resurfacing and put them back together and have a viable alternative to the dastardly difficult to find GM and UAS made lifters.
So I would say if you cannot get real GM or USA made hydraulic lifters, or rebuild the lifters that you have, you might consider not taking a chance with newly manufactured lifters and just go with solids and call it a day.
