I had a question I figured might be worth checking out.
I theorised that nvidia might broadly use the same drivers, but with the 9x branch using a VXD, and the NT branch using a sys - with each being basically a shim to interface with the other shared dlls.
Which might make it possible to make working mixes of later 2k drivers to the last 9x core files.

So I compared the 81.98 9x/2k driver packs.
Unzip uzing 7zip
compare with powershell

1$2kpath="C:\\NV\8198-2k"
2$9xpath="C:\NV\8198-9x"
3
4
5$filesA=(get-childitem $2kpath )
6$filesB=(get-childitem $9xpath )
7foreach ($filea in $filesA) {
8    foreach ($fileb in $filesB) {
9   # Write-Host ($filea.name).ToUpper() ($fileb.name).ToUpper()
10        if (($fileb.name).ToUpper() -eq ($filea.name).ToUpper()) {
11            #pause
12            if(Compare-Object -ReferenceObject $(Get-Content $fileA.FullName) -DifferenceObject $(Get-Content $fileB.FullName))
13
14            {"files are different"}
15
16            Else {
17                "$filea.name Files are the same"
18                move-item $filea.FullName "$2kpath\same"
19                move-item $fileb.FullName "$9xpath\same"
20            }
21        }
22    }
23}

Some mildly interesting findings.

These files are identical between both versions.
Advanced.tvp
CAD.tvp
data1.cab
data1.hdr
data2.cab
DCC.tvp
default.tvp
Finance.tvp
keystone.exe
layout.bin
NvApps.xml
NvCpl.dll
NVDisp.nvu
nview.dll
NvMCTray.dll
nvshell.dll
nvtuicpl.cpl
nvudisp.exe
nvwddi.dll
nvwdmcpl.dll
nvwimg.dll
nwiz.exe
Readme.txt
setup.bmp
setup.exe
setup.ini
setup.inx
setup.iss

These are unique to 9x:
ikernel.exe
NVAML.INF
NVARCH16.DLL
nvarch32.dll
nvcore.vxd
NVDD32.dll
nvdisp.drv
NvInst32.dll
nvmini.vxd
NVMODE.DLL
nvOpenGL.dll
NVRSAR.dll
NVRSCS.dll
NVRSDA.dll
NVRSDE.dll
NVRSEL.dll
NVRSENG.dll
NVRSES.dll
NVRSESM.dll
NVRSFI.dll
NVRSFR.dll
NVRSHE.dll
NVRSHU.dll
NVRSIT.dll
NVRSJA.dll
NVRSKO.dll
NVRSNL.dll
NVRSNO.dll
NVRSPL.dll
NVRSPT.dll
NVRSPTB.dll
NVRSRU.dll
NVRSSK.dll
NVRSSL.dll
NVRSSV.dll
NVRSTR.dll
NVRSZHC.dll
NVRSZHT.dll
nvsvc.exe
nvwrsar.dll
nvwrscs.dll
nvwrsda.dll
nvwrsde.dll
nvwrsel.dll
nvwrseng.dll
nvwrses.dll
nvwrsesm.dll
nvwrsfi.dll
nvwrsfr.dll
nvwrshe.dll
nvwrshu.dll
nvwrsit.dll
nvwrsja.dll
nvwrsko.dll
nvwrsnl.dll
nvwrsno.dll
nvwrspl.dll
nvwrspt.dll
nvwrsptb.dll
nvwrsru.dll
nvwrssk.dll
nvwrssl.dll
nvwrssv.dll
nvwrstr.dll
nvwrszhc.dll
nvwrszht.dll
Setup16.bmp
VGARTD.VXD

These are unique to 2k:
engine32.cab
HPQVDISP.dll
modes.txt
nv4_disp.cat
nv4_disp.dll
nv4_disp.inf
nv4_mini.sys
nvapi.dll
nvappbar.exe
nvcod.dll
NvColor.exe
NVCPL.hlp
nvdspsch.exe
NVEPClnt.exe
NVGFX.dll
nvhwvid.dll
nviewx.dll
nvmccs.dll
nvmccsrs.dll
nvnt4cpl.dll
nvoglnt.dll
nvsvc32.exe
nvsysrot.dll
nvwcplen.hlp
NvwsApps.xml
setup.ibt
setup.skin
tablet.tvp
TOSGFX.dll

Observations:

• There are some files that are not driver files, but are bundled to make installshield run.
• I was incorrect. They appear to be largely separate code branches.
• NV4 which was something I never thought about, seems now to be obviously related to NT4
• A whole bunch of the 9x dlls are simply languages

I'm sure someone has, or will have similar thoughts one day, and maybe they'll google it.
Or maybe someone will decide to dig deeper. Either way, here's a basic starting point.