Exhaust Manifolds

I know that this has been discussed before but why do some people recommend the 360 truck manifolds for the A body small block when they won't fit. I think that it's been said that the right side fits but not the left and for that the 340 manifolds have been suggested but they are hard to find. What about manifolds from the volare / Aspen that had the 360 or a diplomat,etc. Was there a police interceptor 360?