'71 Duster 440 or 360? Pros and cons

i'd go with the 440. u can get engine-mounts,headers and etc u need to the engine in at engine-swaps.com
the heads are ok for performance use as well, i would upgrade to the 906 heads or the 915 heads. u can have those 346 heads rebuilt with bigger intake and exhaust valves to handle better performance.