Can I add an headphone jack to my preamp?

My preamp doesn't have an headphone output, can one easily be added? The headphone impedance is 63 ohms. Thanks
Sure but you need more than the jack; you need a driver for the headphones. Unless you have some experience with adding circuitry an active device, you might best consider buying a stand-alone headphone amp.

Buy a small headphone amp. You can run it from the tape output, or any other output. Far far easier than adding the electronics internally.
I own four headphone amps. Rudistor, Single Power, Little Dot,and a Tadac.
The Little Dot is about $250 shipped via eBay from China, and was recommended in Stereophile. A nice little tubed job.
The Rudistor mkII is no longer available as far as I know. The Single Power is a 'notorious' headphone amp, (Claims of exploding SP killing it's users are greatly exaggerated LOL.)
The TADAC is a DAC and headphone amp rolled into one.
So for a few bucks to two grand... you can get a nice little headphone amp.