C1500 radiator cooler connections question
 

I'm installing a new replacement radiator in my 97 C1500, and have questions about the cooler connections. The radiator came with threaded adapters, which I don't need, and some o-rings. The transmission cooler receptacles have o-rings, which the flared end of the cooler lines press against, when you tighten the captive nut. I assumed that I should leave the o-rings there -was that correct?

Also, the oil cooler lines are the type with a flare and about 1/2" or so of straight tube after the flare. I'm not sure if I just push them in and tighten down the nut, making a metal to metal connection, or if I'm supposed to put an o-ring over the end of the tube and slide it up to the flare. The adapters for that side (which I don't need) have a o-ring near the end, which I can remove and use for those lines. The leaking radiator I took out was a cheap unit, and no o-rings were installed.