1990 Mazda B2200 Truck

1990 B2200 truck. Was given to me by my brother. Lifters were ticking;mechanic replaced several lifters, and no longer was ticking. Lifters started again after couple yrs, so he pulled the valve cover, found most oil holes clogged. Pulled all but front 2 lifters, cleaned, oiled and put them back in. When he cranked it up, it was skipping real bad, which it will till lifters pump back up, correct? It then blew out the rear main seal. This is when he gave it to me.I started it up and it was still skipping bad, and I could not believe how bad it was smoking, but it was white smoke.I let it run for some time, but it didn't seem to help the skipping. He said the gas in it was approx.6-8 months old. Could this be the reason for the smoke and WILL the skipping eventually stop when the lifters pump back up and how long should it take for them to pump up?