Why not gasser rear enging?

My guess is its mostly related to cost and volume. Ford for example builds its V10 drive train for a large variety of trucks in addition to RVs. The more you build, the lower your unit cost. Also, the V10 having been around so long and used in so many vehicles, it has become refined and highly reliable. For me the engine noise is only loud at high rpms in lower gears while excelerating or climbing very steep grades which is a small percentage of my total drive time. For me this was the most cost effective option given that I no longer spend months on road trips and am not a full timer. I think the DPs are a great product but I just couldn't justify the much higher cost. Ford would have to redesign the entire rear axle/drive train in order to do a rear gasser. Probably not worth the cost. Fords truck sales volume probably holds down the cost of their V10 RV chassis and is probably the reason they dominate the gasser market now.