For mule deer and pronghorn, I'd probably pick the 243 Win out of the current Montana line up. Though the twist precludes some of the bullets I'd like to use, I think the 95gr BT and/or 90gr Scenar would be more than enough for either. Second choice would be a 308 to shoot the 125grAB or 130gr TTSX. Out to normal ranges I'd think it'd be a whole lot like a 130gr/270 load...

Might be able to find a used 84M cheap enough that having it rebarreled with a 243 or 260 with an 8" twist would be worth it. Would increase your bullet options.