If you have all the baffles, you have the most important of the parts that direct the air flow. The seals are a rubber-like (they have also been called masticated fillers) seals that are on on the right and left side in front of the radiator. See the bottom two illustrations on the attached diagram from the 1968 Service Manual for where the seals are on the '68. I am not sure if '69 is the same.

I had my original Harrison UP radiator recored and restored a few years ago. I had also successfully run an aftermarket from a classic car vendor for a few years too.

Others here with knowledge and experience with available radiators or, if you have a good radiator shop you can talk with, they may be able to mention vendors and discuss radiator technology a lot better than me. Radiators are not cheap so by consulting with an expert before "trying" a new one might give you the level of cooling improvement you can expect.

Some places advertise by the number of cores and other by the number of rows. Some have original equipment appearance and others have all kinds of designs. Some are copper and brass and some are aluminum. And, occasionally there are original radiators that pop up for sale.