29 years after a rebuild....

I rebuilt it 29 years ago, a mild, mostly stock 340, and it has been strong and reliable. Recently when I saw metal dust in the oil filter. I did a semi tear down and found the valve spring retainers are scuffing the stamped rocker arms. Its been along time and my memory these days is crap. The build is a 69 340 with stock X heads. The cam was a 280ish 474 lift DC purple cam with DC valve springs that were good to 500 lift. I shimmed the springs, I think 005 or 010 to get the height at 1.75". The valve train is stock, and the block was decked an unknown amount to remove surface rust.(unkept spare) I used over the counter felpro blue head gaskets no consideration of thickness.
I know this is a geometry issue, and I'm a general math guy. Any advice on what to check will be appreciated, hopefully in layman's terms would be great.