Reusing lifters

The most important time in a flat tappet lifter's life is break in. Once broken in and a wear pattern is set in, they are good to do. While it's certainly true they all do wear to their individual lobes, I wouldn't hesitate to throw them all in lubed up with ZDDP and bust it off and let it run on high idle for a few minutes. I would inspect them all first. What you're looking for is evenness of wear and none dished. If they all look acceptable, you probably won't have an issue.