In general, for heater cores, best to get OEM. some people recommend copper or brass
I did put a NAPA in mine (turned out to be aluminum when it arrived, I put it in anyhow), had to fuss a bit to get the air seals right (so it wasn't a perfect replacement), but works ok.
'89 Wrangler YJ
97 Grand Cherokee (ZJ)
87 MB 560SL roadster