What size tires are you running?

A larger diameter tire may do what you want and will probably be cheaper . . . not to mention easier.

Measure the diameter of the tires and compare one against the other as a factor of percentage.

Figure as well the percentage factor of a gear swap you're contemplating so you can make a direct comparison.

Generally speaking - and I'm sure the math police will correct me if I'm wrong - a 3.50 diff compared against a 3.70 makes for about a 5% change.
A 30" diameter tire compared to a 28" diameter tire is roughly 6% different.

All of which means that making either change will change the engine rpm the percentage gained by either the gear swap or tire change.