Just looking at it logically, the FE snorkel should be longer because those motors are wider than a Boss 302.
I'm wondering what you have now too since looking at your pic again and seeing the smaller footprint mounting flange like 428, but the secondary S tube adapter like 390 (or others? - that is the question.)
Need more pics and measurements.
The only snorkel I have kicking around is for a 69 351W 4V.
Your air cleaner bowl does have the correct metal pcv elbow.