Whatever visually appealing (and actually available) wheel/tire combos anyone cooks up still have to pass a practical "fit" test. You seem to be fairly set on the rims you want and both of them (front and rear) have zero (0) offset. Rear fitment is most critical on first gen Montes as there is limited outboard room (between the outside tire sidewall and the wheel opening lip of the rear quarter panel). Positive offset on the rear rims is usually needed with wider tires to move the wheel/tire assembly inboard where there is considerably more room. Of course, you can also trim the wheel opening lip if you are forced to and don't mind modifying your Monte's sheetmetal.
You have stated that you are currently running 225/70-R15s all the way around and from the photo you provided it appears that they are mounted on stock 15x7 rallys. If so, the offset on those factory rims is +.30" (+7.62 mm). Now, if you go to https://tiresize.com/wheel-offset-calculator/ and enter your current tire and rim offset data into the "Original Setup" boxes, then you can enter the specs of whatever tire you want to compare (using 0 offset for your chosen rims) and visually see how they compare. Further, the box on the upper right will show you the exact dimensional changes to clearance outboard, above and inboard.
I ran the comparison between your current setup and both the 275/50R17 and the 275/55R17 tires and found that either tire will cause your current sidewall clearance to be reduced by 1 1/4". You can easily check the clearance of your current setup to see if you can afford to give up a full 1.25". If not, you will either need rear rims with enough positive offset to give you more clearance (each +6mm offset = 1/4" additional backspace) or you may need to trim the wheel well opening lip. (While I have never done that, I have heard that 1" is the practical maximum amount that lip can be trimmed.)
I run 275/60R15s on 8" rims with 5.0" backspace (+13 mm offset) and I have only 5/8" (.625") sidewall clearance to an untrimmed wheel well opening lip. If I mounted any 275 width R17 tire on your 9 inch 5" backspace (0 offset) rim, my outboard clearance would be reduced by 1/2" to 1/8" (.125'). That may be enough sidewall clearance for some folks, but I would never take that risk.
Your call, of course, but you don't have to guess. Just compare future tire choices to your current wheel/tire setup using the specs of your desired rim and visually see the actual physical comparison using the tiresize.com wheel offset calculator. Good luck.