It's almost my birthday ( parts time)

I know they use them (chain tensioners) in stock Magnum 5.2 and 5.9 engines so I wouldn't think there just a short term item. I realize that stock engines aren't race engines but they last well over 100,000 miles before needing replaced. I'm using one in my 360 just cause small blocks are bad about chain stretch even if you use a good chain. I pulled it back apart after 700 pretty hard miles to swap the cam and it looked just like the day I put it in. Sorry I don't know the part # but if you go to www.manciniracing.com I'm sure you can find the part # there.