Dave Sims is well aware that most people don't land their dream job in their 70s. 

After 18 years calling games for the Seattle Mariners, Sims thought he had already found the job that would be the highlight of his career. He had achieved his lifelong sportscasting goal of having his own team, and after nearly two decades in the booth recently earned a nomination for the National Baseball Hall of Fame's annual broadcasting award. 

Indeed, if he retired today after a 50-year career, the play-by-play caller tells CNBC Make It that he'd "be pretty proud" of how his professional life has gone.

"It's exciting," he says. "You don't think, as a young Black kid growing up in Philly, that you're going to end up the voice of a Major League team." 

So when WFAN offered Sims the New York Yankees radio job after John Sterling announced his retirement last season, he could hardly believe it. 

"I was talking to a friend the other day about, if I were to write a letter to eight year old Dave Sims back in Philly and said 'Eventually you're gonna grow up and be the voice of the Yankees,' I can imagine the response would've been, 'No expletive way. No chance. Are you nuts?'" Sims says with a laugh. 

Though he didn't expect to wait so long to receive his biggest career opportunity yet, Sims is excited about becoming the voice of the Bronx Bombers. The septuagenarian is a regular at the gym, taking care of his body to, as he says, "squeeze as much juice out of the orange as you possibly can." 

"I love the excitement of baseball and I love the gig," he says. "So the fact that this came along at this time in my life is pretty remarkable. I'm quite grateful for it." 

Sims is feeling healthy, and he tells Make It that the next few years calling Yankees games may actually prove easier than when he was broadcasting in his 60s. That's because Seattle's geographic placement means the Mariners travel many thousands more miles than most other Major League teams. 

The Yankees will travel roughly 32,000 miles this season, while the Mariners will log a little over 44,600 miles between March 27 and September 27. 

It's a busy schedule, especially for a 72-year-old, but Sims hopes to remain healthy and energetic enough to do the job for a long time. 

"A lot of guys this age say 'Man, I can't wait to get the hell out,'" Sims says. "But I can't wait to get to work."

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