I have accomplished any improvement I can see using the e28 radiator, by simply having my e12 radiator re-cored for around $100. Since the tanks on the e12's are metal, any good radiator shop can do the job. Don't get tricked into performance radiator talk. Often times an increased row of tubes simply reduces the air flow over the other rows. Stock is just fine, even if you plan on boosting engine performancc. This is not an area that BMW engineered marginally. If you are having trouble with your 20+ year old radiator, that is not a surprise, and most of them cannot successfully be "rodded" out. Recore it. It will be the same as buying a new one. If you have trouble in this area, find a radiator shop that is "Behr" certified (a manufacturer).