I am afraid there is no correct answer to this question. Many factors affect how fast your older Class C Motorhome will climb hills, such as are you towing a vehicle or trailer behind the Motorhome, is the Motorhome overloaded, how steep of a hill are we talking about, what altitude are you at when you are climbing the hills, etc.
The first thing I would do if I owned this Motorhome is take it in and have the engine compression checked. With 107,000 on a gasoline engine there is a good chance that you will have compression problems. A lot also depends on how well the engine on this Motorhome has been maintained over the years.
If you have the engine checked out and the compression and all else is fine, then I would suggest that you have it tuned up and see if that helps. I need to forewarn you that in all likelihood there may be some issues with this engine that may require an engine rebuild.
Sorry I could not give you a more specific answer to your question.
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