Pre-lubed Hydraulic Lifters
I prefer not pumping them up beforehand, my current 360 Mag has stock Magnum roller lifters which call for a lot of preload (.080-.095") and with my cam and stock Magnum pistons it's a bit tight on the P-V clearance. When I first assembled it some of the lifters had pumped up on their own somehow (probably from leaving them in the block for a long time with the rockers and pushrods removed) and I had to carefully rotate the engine slowly by hand until they pumped back down as some of the valves were contacting the pistons.
That engine is still going strong after 3 years and about 8-10k miles...