I just got a johnson acoustic/electric and i'm not sure what kind of strings it uses. The model is JG-650-TN- I tried putting some Martin 80/20 bronze strings on it but they didn't fit. Any help would be appreciated. thanks
You should be able to just put on whatever strings you want. I've never heard of a situation like this.

PS: congrats on picking a Johnson. I have a Johnson Catalyst, and I think they make great, underrated guitars.
I put them on, i was wondering if i put them on wrong but it seemed right. The strings weren't very close to the bridge of the guitar when i put them on, i never had that problem before either. Maybe i will just have to try to get some different guitar strings.