I just finished a 29 model A...
I had pictures for mine...my friend took them of his fathers A. I couldn't find ford engine green either. But, I got it spot on by combining dark green, turquoise, geman uniform gray, and a light cammo gray. Now, I was able to get to that color, but I just did it with the colors I had at the time. Lemme see if I can find you a picture of the color.
This one is a little hard to see - http://www.eastwoodco.com/email/default.asp?T1=10056Z&SRCCODE=1CJBAN8
This one is better...the bar on the left side...scroll down to engine paints, and you'll see ford green - http://www.duplicolor.com/products/colors/highheat.html
Hope this helps!!
-jonathan