Performing a search on the site will bring up more threads on the subject and you’ll see that opinions vary widely on this subject. From my own perspective, used lifters being moved from one block to another is a substantial risk. There’s already enough risk in using new cams and lifters without increasing the chance for failure by using used lifters from another engine. From a shop’s perspective, the risk is simply too high to provide any kind of warranty that could cover this. If I had to use a camshaft from another engine, I’d at least put new lifters on it to reduce the amount of risk of cam lobe failure. Valve spring pressure also plays into this and an increasing of the valve spring pressure over the stock values compounds the issue.