Yes, you will be able to climb again. And you will be able to go fast.
Exactly like you did years ago? Maybe or maybe not, but it doesn't really matter. Most of us find other satisfactions in and reasons for riding besides how fast we go or how quickly we climb.
I started riding at age 58, and within 4 months I rode the 350 mile "Ride the Rockies" over Colorado passes. Given decent training and miles, your body will surprise you.
We have folks here who race regularly in their 60's. We have folks who love leisurely riding, folks who go on long self-contained tours, folks who mainly enjoy 20 milers. You get to find your niche and develop that aspect of your bicycling.
Look a SaiKaiTai, who joined with us 2-3 years ago, and is now climbing very difficult grades, even with a significant heart condition.
And it's haaaard, yes it is. It's haaaard, yes, it is
All is possible.
Mostly, have fun.