You may or you may not. We have no idea what rad you are running. 2 row, 3 row, 4 row, what tube size?
Check the T-stat like I posted first. Just to rule it out. Then make sure your fan is working. On my 1970 Firebird, with a 455, the electric fan stopped working, but temps were still okay when cruising, due to airflow across the rad. At idle, temp crawled up quickly. Make sure those are both working before you move onto the rad as the culprit.
This is a fixable issue. You just need to work through the problem.
