If I were to do SPI over LVDS, do you need to make each pair separate with a shield? Or, could I just get one cable with the correct pairs for each signal and just shield the one cable?

 

The need for shielding depends upon the noise, or lack thereof, in your environment.
http://www.ti.com/lit/an/slyt163/slyt163.pdf

 

From the example, it looks like it is just one cable. Thinking about it, ethernet is differential pairs and one shield (is that correct?). Multiple cables seems rather excessive....

 

What is your SPI Clock Rate ?
How far ?
How many SPI Slaves ?

Ethernet is high speed at 100 meters

 

I am talking 4 feet....so nothing extreme....
5 spi slaves
clk rate is probably 4 mhz, but i can go slower.

 

Cat-5, 20 mhz, 9 feet = 0.4% Jitter.
Less than 5% Jitter is acceptable.
Less than 6db loss is acceptable.

LVDS or M-LVDS ?