I have the opposite issue, My right leg is
shorter by 12 mm.
I wear a 12 mm lift under my right heel in all my street shoes and the biggest lift that works with my cycling shoes. Under the ball of my foot I shimmed put the cleat with 6 mm (1/4" aluminum plate. (Bending it to fit the shoe curve was not easy!)
The shimmed shoe works really, really well! Bike feels completely "right". For the first time ever, I look down right through the center of the bike.
Don't go with unequal cranks. Shim your cleats (if you ride with them) or put a lift under your foot of 1/2 the leg length difference. (And more under the heel to the full difference if the shoe still works.)
The lift can be an insole or just as effective, additional thickness to the sole. I got the diagnosis and recommendations from cycle Oregon's PT. Life changing. (My legs are a QC issue. Since I never had the chance to use anything else I was clueless. Went to the PT for entirely different issues. First 5 minutes she had me walk the room away from her and back. "Your right leg's shorter." Sent me home with the 12 mm lifts, same as the difference in leg length, to put in all my shoes. (Shoes are different so I use different kinds for different shoes but all 12 mm. Had 2 re-soled.)
That was 10 years ago. I now take standing straight and sitting straight on the bike for granted, Until the lifts, it had never happened. 5 decades of crooked. (I ride 175 Sugino 75s but 1) they have 20k miles on them and 2) you aren't prying them (or even just one of them) from my cold dead hands. And I will never go with unequal cranks, at least not for this issue.)
Ben