If the new Weavers have the same model designations as the originals, you'd actually be looking at the K2.5. The K4 would be a four power.

My 70s vintage 444 Marlin had a K4 steel "El Paso" Weaver on it when I got it used about 25 years ago. That scope has been on a sporterized03AI for almost that long now, as I wanted a peep sight on the Marlin. Also have a similar K2.5 on a 22 Hornet, both scopes still work fine.

I hear pretty good things about the new Weavers, wouldn't see anything wrong with one of themon the Marlin for bears. Critter acquisition is pretty quick with either the K2.5 or the K4, in my experience.