running hot

So I've been driveing my dart a little bit not much, at idle it will not over heat sitting in the driveway, but when I take it out, for a spin it gets hot and over heats. It never had any problems before I put a 4 inch stroker kit in it. It still has the original radiator the car came out with, it's a 318-68-270 dart. I will be getting rid of the automatic and installing a 4 speed real soon, just need to gather up the parts for the zbar and yoke for a larger 727 trans as mine is a a-904. I am wondering if getting rid of the automatic will help the radiator cool better as there wont be warm trans fluid flowing through it. If anyone else has come up with a fix for this please post. I am figuring a larger radiator and a higher flow water pump and high flow thermastat will be what I need to do. Will a larger radiator from a mopar that had a big block in it work? Or will I have to get a aftermarket radiator and fans $$$$$. I was hoping to make it to my first car show this summer, to hang out and drink some beers, with some good car guys but the drive is to far to make it the way it's heating up.