DT175 Tire Replacement

Bike in question:


Rear is a 3.50x18 and front is a 2.75x19 .. Doing the conversion 3.50 ends up being a 90 tire where the 2.75 is a 70 tire.

For the back I'm figuring I could do a 100/90-18 and for the front I could do a 90/90-19 setup?

Anyone see any issues with this?