"Keen "to replace V6 with inline Gas engines

Back in the day when flat heads and two valve wedge heads were the norm, intake and exhausts on the same side was the most common setup with inline engines. Now such engines are rare if they exist at all.
When the great majority of inlines use some combination of pent roof or hemispherical chambers, double overhead cams with two or four valves (sometimes 5 valves) per cylinder, they have to be cross flow heads. Even my 24 valve I6 Cummins has a cross flow head.