[jsb5717]

1. If my Montana is sitting stationary for 4 years the factory tires are probably best replaced before traveling on them? Yes, I would replace them

2. What size of Sailun tires would you replace them with? With the same size that's on there now

3. Is there a best place to buy them? Price? I bought mine pre-Covid so not sure about current pricing. I would start combing the internet and find your best delivered pricing. There are places that will mount them for you