Finally replaced my Radiator!

After two months of unconsistent high temps (220F!) and having to shut-down in transit twice the other day, and trying a flush treatment, at 205k miles I KNEW it was shot. I guess I'm lucky I didn't blow the head gasket, but that's where experience saved me, knowing how easy it can happen I always killed it at 240F.

So I went to the junkyard this weekend and found a like-new radiator for $38. Changed it in myself in about an hour. The hardest part was getting the lower tranny line off the old rad, it was ON THERE! Not only is it running very cool now but I have regained ~15hp, the old rad was SO clogged the water pump was working triple-overtime and robbing power from the motor. Now It's like a new car!

Question: Now that I don't have to worry about it over heating SHOULD I put the thermostat back in? It stays below 140F when driving, but stopped it will slowly get to 200F on the fan will kick on and have it back down to 160 in seconds, like when I bought the car. I don't mind using a little extra gas with a cold motor but will it hurt it over time running that cold?

I would certainly assume it would slightly damage it over time yes. Otherwise they wouldn't have made the car run at that temp would they?