I think you don't need any special stuff, the Blue&White Yosemite G3 just happen to come with built-in SCSI but was IDE ready, albeit the IDE chip was kind of flaky and was prone to fail on first revisions versions.
Worst (not that worst as you will read later) case scenario, you would need to buy a PCI card like
this one which is rather good for your system giving it a hard disk speed boost, you would attach the IDE hard disks to it, and giving you the ability to use up to four larger than 128 GBs hard disk each.
In a nutshell, no need to replace the SCSI since IDE hard disks use a different connector inside your Power Mac, needless to say you can indeed take the SCSI out if you feel like it is a waste so to speak.