I have bought a generic after market radiator before that was supposed to fit my car, and it didn't. In fact, it was crap. If you are going to buy a new radiator I suggest you take the plunge and upgrade to an aluminum, and get one from DeWitts here on the forum. Honestly one of the best mods I ever did to my car and it was easily worth every penny. True direct fit drop in installation, and it cools way better than my stock one did and SO much better than the crap one I bought off of Ebay.
When I did my car mt radiator needed attention too, but I thought some of the radiators I looked at were junk so I took the original to the shop and had it rebuilt for 299.00. No fitting issues, and my car always run cool plus I still have the original radiator. My .02 cents.
What is in the lines..transmission fluid or coolant?
Transmission fluid. The lines carry hot transmission fluid from the transmission to the radiator, where there is a tank built into the side of it. The fluid is cooled and returned to the transmission by way of pressure from the transmission pump that sends fluid to the radiator.