From what I understand when you put an excelerator card in the older mac,it will increase the bus speed. Although, it may never get over 50 mhz.
Yes; almost all accelerators set the system bus to 50 MHz.
I guess then the question would be if I would have to use a serial console?
With a PCI ethernet card and a PCI IDE or SCSI card, you'd have one slot for a video card, but the serial consoles are a lot easier.
John