kz650 forks

I have a 78 kz650. one of the forks is leaking, so obviously needs new seals. I have a couple questions. is there anything else I should fix while putting in new seals? what forks will fit off new bikes, if I decide to go that route? I appreciate any help

What else is broken?

If you're just looking to "freshen up" the front end while replacing the oil seals, my suggestion would be to replace the OEM roller bearings and races with a Tapered steering bearing and seal kit .
The OEM steering bearings have a tendency to get pounded into the races from driving on rough roads and hitting potholes over time, and will leave "dimples" in the races that will cause a "notch" in how the steering feels when turning.
To test if the races are notched, elevate the front wheel slightly off the ground, then slowly turn the handlebars from side-to-side. If it feels like the wheel loosely "locks" into position facing straight forward, then the races are notched.

Even if the steering turns freely, those are 20+ year old bearings/races/seals there. Upgrading to the tapered bearings will give you the comfort of knowing they're new, plus they help the bike steer/handle better. They're only $36 (plus shipping), and you can install them yourself with simple tools while you're having the seals replaced.
Even if you're replacing the fork oil seals yourself, this is a simple weekend (or one day depending on your mechanical ability and available tools) task.

And while you have the front wheel off, it sure couldn't hurt to examine the wheel bearings and seals to see if they're also in need of replacement, or at least being repacked with grease.