cooling not so cool

Running warm, use the back of your knuckles, or these days, a temp gun, and measure the temp of the rad, mid way down, slowly, all the way across.
You'll likely find some cool/cold areas, the more cold tubes, or bigger cold area, the bigger the prob. The cold areas are blocked tubes, not doing their job.
Have the rad rodded out, or re-cored, latest rage is alum.
Use the heat gun to measure the temps at the rad inlet/outlet temp, the rad should lose min 40 - 50*.
Then go take the same readings off your daily driver for comparison.