When setup gets to setting up hardware on Windows 95 Build 431 and also Windows 98 Build 1400 It says
"The file buslogic.mpd on Windows 95 Disk 6 could not be found"
"Insert Windows 95 Disk 6 into the drive selected below and click OK"

What I have tried

Extracting the file from WIN95_06.cab and placing it on a floppy disk image
Googling the file.(mostly untrustworthy sites+surveys)

I can continue to install these builds just fine.

That's "normal" yes. It may ask for other files also so it can be handy to extract all files from the cabs and put it in a separate iso.
The problem seems to be that during that stage of setup windows doesn't mount the win95 cd, so it can't access the files.

I am now on Windows 98 build 1400 Where I have no CD-ROM support.
I am going to try finding "acpi.sys" and coping it to a floppy disk image
Cannot seem to find acpi.sys in any of the memphis cab files

The most simple solution to this is to copy the folder with the CABs to the HDD before installation

Another way to fix this would be to boot from a proper boot disk before allowing Setup to restart into Windows, copying the CD-ROM driver files to the hard disk, and editing CONFIG.SYS and AUTOEXEC.BAT (again, on the hard disk) to load the CD-ROM drivers.

Then, remove the boot disk, and restart the system, and it should work.

Try installing that hardware when you finish installation of Windows. I have got the like that when installing hardware and I installed hardware after installation.

Try installing from hard disk. Copy files to harddisk to a folder you have created.