Yes, early forks had drain screws, the '93+ did not.
FYI, I recommend replacing the 40mm '85-'92 forks w/the '93+ 43 mm forks (the later calipers and rotors need to be from a '93+), you need the triple trees too, but the other stuff can re-fit. I think $$ spent on the early forks is better-spent going w/the larger-dia. pieces, and doing valve emulators and different springs on those instead.
If you decide to leave the fork caps in, and to use the drain screw ports as vents, be sure to remove the fork legs from the triple trees, and to position the drain screw hole, now-open, at a 12 0'clock position so it allows venting. Of course, if you remove the drain screws and drain the oil, then supposedly, you're vented to the inside of the fork leg. However, I don't know if retention of residual oil may still seal-off somewhere in the damper rod an area of air, which could compress from heating. Remember Boyle's Law. Water expands to 1,700 times its volume when it turns to steam. Oil, I dunno, but I'd assume the change is similar. Better to be safe than sorry. If the drain hole starts throwing a column of vapor like The Little Engine That Could, time to cut the heat! And I'd wear something padded and long-sleeve, an OSHA-face mask and gloves.