Side lights

It's actually harder than it sounds; the '69 cars (w/reflectors only) have no actual hole behind the side reflectors to allow for a bulb socket and wire, and the '70-'71 sidemarker light + reflectors aren't the same size/shape as the '69 items.

There are other ways around this, depending on what the OP wants/will accept in terms of finished appearance, amount of work to do the job, etc.

The law requirement was lights and/or reflectors for '68-'69, then lights and reflectors from '70 on. The lights and reflectors do different jobs in terms of keeping you out of different kinds of crashes; light + reflector = best odds of not getting hit.