I hate to repeat my post from 5 posts above, but... just get a PATA drive. I was where you are however many months ago, convinced that I would somehow get my clever AM2 contraption to run Win98 SE on SATA.
I went exactly nowhere. Probably installed 98SE 20-30 times with a whole range of BIOS options, different failure modes, various attempts at various rloew patches, etc. Installed XP to test the machine and it ran beautifully, but... ummm... I already have 2 retro XP systems, why would I want a single core AGP Athlon to run XP?!? Finally I listened to someone here and shoved my SSD onto a Startech SATA to IDE adapter. Got much further than I had ever gotten before. Then I removed the SATA optical drive and bought a NOS PATA one from eBay. (Oh, and reduced the RAM) Boom, problem solved, working 98SE AM2 system, no monkeying with rloew patches, no anything!
I spent months on this, there isn't a huge record of successful 98SE installs on AMD SATA. There's more on Intel ICH5 but those have a special BIOS option for 98SE compatibility. And if anything, your chipset is more rare than my VT8237A or whatever it is, which is a south bridge that was used on tons of 754/939 systems. Maybe even some late socket A boards, I don't know...