N series vs R series

The R7 replaced the N7 but was made I think for only one year, then was replaced by the R70. The R7 still had the large allis engine but the body had the green stripes like the R70. I owned an N6 before going to the R7. I really like the bigger engine and slower rpm. R7 is built much heavier than the N6 but not sure about N7. The main shaft bearings are bigger for one thing. Most other things are the same as the late N models except for the dual spreaders which was not much of an improvement. I have heard good and bad about the Duetz air cooled engines, seems like they are good until you start to have problems, then look out. Some concerns about the availability of parts for the Deutz. I have a 25 foot head on my R7 but know it would handle 30 but a neighbor with a 30 says he would not buy another 30 foot header without haveing duals. Just my 2 cents