LowChevy2 aluminum is way better. I have run both in my 71 nova. You need to watch out for Electrolysis because it can quickly ruin an aluminum radiator. Read about it and how to avoid it at this link to Ron Davis Tech.
http://www.rondavisradiators.com/tech.htm It shows how to test for it before you have a prob. I could not be happier with my RD radiator They use the stock Nova radiator mount and just drop in.
David