Brass brazing rod and lots of it. We had the chain come off last year and suck the back of the tin back onto itself and ripped the bolt holes out. We pounded it straight, brazed washers over the ripped out holes and brazed the cracks. looks good as new. We need to braze patches over the corners of the ear savers and fix some more cracks. The key to brazing is clean metal, no rust, and the right temperature with a small tip on the torch. I looked for aftermarket poly tin and none is to be had for the lM black heads. lots of red and green options for poly. We have a 6 row G orange head with nearly new tin but it is different. Jason