Here is the simplest method I've found for installing 98, but it does require that you can connect the drive you plan to use to a modern machine. You'll also need Windows 98 ISO and a copy of DOS, as well as "HP USB Disk Storage Format Tool". All of these are easy to find and download.
Connect your drive to modern system, if the drive is IDE you'll need an adapter to SATA or USB
Run DiskPart and use the clean command on it, as well as convert mbr
Open HP USB Tool, point it at the drive you plan to install 98 on, choose Fat32, Quick format, and "Create a DOS startup disk using system files located at..."
Point the DOS startup disk option at the copy of DOS you downloaded
Format with the tool
Now explore the Windows 98 ISO you downloaded and copy the Win98 folder
Paste the Win98 folder onto your newly formatted FAT32 drive
Connect the drive to your old hardware and boot-up
It will boot into DOS, type in cd Win98
Type setup
Windows 98 setup will begin
This is pretty much full proof, installs 98 much faster than off of a CD-Rom or floppy, and doesn't require anything special from your BIOS