[1malo68]

When new cams and lifters are installed in a new motor, they seat to each other. If you put new lifters on an old cam you run a big risk of flat spotting your cam. I've seen this happen a bunch of times. I always look at cam and lifters as one component...If you change cams, you should change lifters and if you change lifters, you should change cams so the components can seat to each other. It's more expensive but you will only do it once.
As far as adjustment for a hydraulic flat tappet valve train, In my opinion, the most reliable, one time, way to do it is: Soak the new lifters in oil overnight and put the #1 cylinder at TDC on the compression stroke. Spin the pushrod on the #1 Cylinder between your thumb and forefinger and tighten the adjuster nut until you BARELY feel a slight drag on the pushrod. Tighten the adjuster 1/2 turn and repeat for both the intake and exhaust valve on that cylinder. Rotate the crankshaft 1/4 turn and repeat the process on the #8 cylinder. As you complete each cylinder, rotate the crank 1/4 of a turn and do both valves on each one. 1/4 turn on the crankshaft brings the next cylinder to TDC on the compression stroke. The order will be 1, 8, 4, 3, 6, 5, 7, 2. You won't have oil slinging all over the place and you should never have to adjust them again. Just my $0.02.