Nope
Yep. We have a 350 and have friends with a 390. We raft together frequently and have walked the gunnels comparing. They are identical with only a few exceptions. The exterior is absolutely identical
Stern Cleats:
-> 350 are mounted on the transom
-> 390 they are inboard with hawses on the transom corners
Handrails:
-> 350: Aluminum
-> 390: SS
Bridge Salon:
-> 350: bench seats
-> 390: Bench seats with two semi-circular backrests
Salon:
-> 350: small semi-useless 'desk' on stbd inside of slider
-> 390: No desk, small shelf instead.
Galley:
-> 350: surface mounted cabinets
-> 390: Flush mounted cabinets
dish storage in port shelf beneath port windshield
Guest Berth:
-> 350: Full size bunk
-> 390: Twins
Master Berth:
-> 350: slightly smaller island berth
-> 390: Slightly larger berth
Taller cabinets
Bow:
-> 390: Samson Post
Windshield:
-> 350: 2 windshield wipers
-> 390: 3 windshield wipers
Gelcoat Color:
-> 350: white
-> 390: a touch of a cream color (side by side, the 390 is has a tiny hint of beige compared to our 350).
