Is it possible to get a lower ratio than a 3.54 say a 3.38 or even lower

Only it you have a custom crown wheel made. There are companies that do this sort of work, but as you can imagine,they are not cheap! 3.54 is the lowest ratio available from Ford.

3.54:1 is longest/tallest ratio.
Normally the term lowest ratio taken to mean the shortest ratio which is some like 5.2:1.