old setup - 275/70/18 on stock rims
new setup - 305/65/18 on 10" wheel

I just bought my wheels and tires recently. I will have them balanced tomorrow and will pick them up. Monday, I will install the 2" level kit and mount the tires. My question is: what do I need to do next with my truck after the modifications have been done? Speedometer change, gear ratio, etc?

 

Those are all good things to do, but you don't have to do them, depending on your truck. What gear ratio and engine you have? If you have a small engine with tall gears, a gear ratio change might need to be made.

 

You will need to have your front end aligned after installing the leveling kit