The poor ole thing is 37 years old! You could give it a hug, make sure it runs well and ride it as is. As for customising, it depends on what you want to do to it and your skills, as there won't be much you can easily get that will bolt on.
I purchased a '79 basket case years ago. I had a S&S stroker kit added to the engine. Then, of course, I had to upgrade the brakes, so I could slow it down. I painted the frame and tank, fenders & side covers. It pulled like a freight train with the stroker kit. I surprised more than one big twin in a roll-on. The torque of the stroked engine was very satisfying! I rode it for ~10 years and then sold it.
I had one of those. The big issue with it was the rear exhaust. HD mounted the rear master cylinder high up on the rear sprocket cover. You can take the sprocket cover and rear brake line off a 1980 and then you could use the exhaust from other years. Outside of the motor you could use parts up to 1990. It was also the last year for a kickstarter.