I would change the hose, as it may have hardened in the shape of the old rad.
There are some deluxe clamps on the internet eg Demon Tweeks.
When I had a persistent leak on my Roadster, especially in cold weather, it drove me mad for weeks...…..even deluxe hose clamps, and PTFE tape. It turned out that the metal pipe, which wasn't on the rad by the way, was out of round. I did the best I could in the vice, and managed to stop the leak, but sometimes it can be hard work!
