I put a '92-'95 Civic 3 core Fluidyne radiator in my '92 CX / B18C1 hybrid. The car would start to overheat on the stock single core radiator when running high speed (90's) on really hot days for long periods of time. With the Fluidyne, it never moved. I think paid around $400 for mine but I bought one of the first ones, I think they're closer to $325 now. Great quality and I still have mine in my '98 EX till I get rid of it.

You will want something to block the other side of the opening if you don't have an A/C system though, otherwise the air just goes through there rather than your radiator.