For all those bringing up his maximum HR - please be aware that some of us DO have medical / heart conditions and/or take medications that will limit your maximum HR.
OP - when in doubt, consult a cardiologist. Possibly request a stress test, and ask an actual
medical professional (rather than internet forum posters) what is best for you.
I know of one cyclist, many years younger than I, who pushed his HR on a hard climb, and suffered a full blown heart attack on the descent.
If you want to check your gearing, go here:
Sheldon Brown's Bicycle Gear Calculator