Yes and no. We have built many of the 4 and 6 auto and marine engines and they many times are the same
However corrosion on raw water engines is your enemy. Also the 4 cyl has two versions a 120 rated H.P. engine and a 140 rated H.P. engine. The 120 usually had the siamese intake port head whereas the 140 usually hade SEPERATE or 4 individual intake ports. the 140 was a better head but intake and exhaust manifolds are not easy to adapt to auto use.
Could be doable bot could also be quite a bit of work. Good luck, hope this post helps
Brad.
