Motor Scrapers, 613 and JD 760A

Been thinking of adding a motor scraper to the lineup. We wouldn't use it a whole lot, so we were looking for something older but had a reputation for reliability. The old 613's seem to be priced right. Any experience on them? Also know of an old JD 760A anyone with any experience on them? I had heard once that the 3 axles were good for finishing. What would be a comparable Cat 3 axle and what are the parts availibility of these machines. Would prefer powershift, but what were the earlier gear drive options? I assume the powershift is a big upgrade. Any difference in loading, would prefer the one requiring least assistance to get full. Thanks.