tips/advice on flex head for M2 - is this decent

I'm growing soybeans for the first time and am looking for a 15-18' flex head for my late 70's M2. There is one local (Central NY) that I looked at - it looks to be a late 70's model as well. It is in decent condition but I am wondering if these heads worked well or if I should be looking for a later model L/M header. I see on partsbook that they seem to changed significantly in 1984, specifically the skid system under the cutterbar. I'm going to be doing around 50acres a year and planting them on 30" rows.

Thanks!