I have an early VIN# 1988 that I've been chasing an intermittent air pocket issue. I finally found the issue. My expansion tank is leaking very slightly at the top of the inlet nipple, and that's drawing air in as it cools down. I brazed the nipple to the tank for now, but I really would feel more comfortable replacing it. And that's the problem. I've searched all over and that brass tank that I have has been discontinued, the used ones that I have found all look sketchy at best, and I found one place in the UK that wants $400+ US for a NOS. Can I retrofit the tank to a plastic 1990-94 reservoir or am I stuck? And if I can go to the plastic type, what do I have to do to fit it/plumb it? I hope one of you guys has done this swap before.