Actually this one (it's a thinkcenter E50 8772 - 78G) was a pig to install 98 on - would only boot into safe mode until I followed advice here
https://www.vogons.org/viewtopic.php?t=41065 - specifically "Disable all 32-bit protected-mode disk drivers".
I then managed to find the correct IDE driver and it now seems to be working OK, although there are a bunch of unknown devices in Device Manager. I didn't manage to find a full set of drivers for the machine anywhere, for any OS.
(edit: I take it back, XP drivers but not windows 98, are available here:
https://download.lenovo.com/eol/index.html)
Only irritation it that although it now has USB disk support (I installed nusb36.exe) external drives oddly show up twice, with two drive letters assigned.
Oh, and sometimes it seems to momentarily hang before disk operations. Still, generally speaking it's a speedy and practical machine.