Odied,
Just want you to check things out.
I had a stock 250 in a 67 chevelle, bought it after sitting for years. Started driving it regularly and it developed a bad tick, pulled the valve cover and found a broken valve spring.
Simple fix.
Your engine will have many more miles of stock use in it. But when you start pushing it harder, those 40 year old parts will let you know they are past their limit.
Lets figure out what the problem is. Tom