SCSI drives seem to be quickly disappearing. Those that are still around seem to be wide and/or ultra SCSI.

My PCC PowerTowerPro (October '97) has an older hard drive with the old, wider 50-pin SCSI connector. Can I replace it with an UltraSCSI drive? Still 50 pin connector, but more densely packed. (Obviously I'd need some sort of adapter.)

Any other suggestions for easily replacing a drive in an older machine?

Where I work, we have a number of Power Tower Pros. Some of these do have ultra wide drives. Depending on your vendor, you may get an adapter thrown in. The only REAL difference in the old and new (apart from speed) is that the wides support more devices in a single chain (if you have the card for it, of course).
But, I digress. YES throw it in - it should work fine.