What is the firing order on a 2 up 2 down engine?
It would depend on the cam but it has to be 1324 or 1423.
Here is a current thread on the engine:
Ed Winfield went with 1324.
Jim posted this link
on the other thread and if you scroll down to the bottom of page 9 of the PDF (page 26 of the original) you'll find the information.