Your Yanmar had 21-HP when new, but it is not new now. You probably have 16-HP now. On the positive side, it is a relatively heavy tractor for its horsepower, and weight is eternal.
Your tractor is about 48" wide at the tires. A five foot Landscape Rake will protrude 6" at each side, when pulled straight. However, most of the time, you will use it on an angle, to move dirt across its face. On an angle, it will just cover your tire tracks. This is the correct size rake.
((When angled best results will be achieved if the trailing end of the rake is higher off the ground than the leading one. This allows the end of the rake closest to the tractor to rake heavier than the end farthest from the tractor, creating a better screening action as the material moves across the front of the rake.) The vibrating action of the Rake Teeth breaks up sod and mulches the soil. (User tip: The faster you can go the better the vibrating action will be.) Pulverized soil passes between the teeth, while large stones and debris are gathered into a row. This screening action produces an ideal finished surface, ready for seeding or sod.))
In terms of the cultivator, you know your tractor and soil best, not I. A four foot Cultivator will have
five tines in the dirt. That is quite a lot of draft, the jargon we use for soil resistance to your tractor's pull. That is considerable resistance for the 16-HP in the Yanmar to overcome. Also, you do not want to stress your twenty-five year old three point hitch to the point of breaking something. How is the tread on your tires? Does your 4-WD engage?
Have you determined if your Yanmar three point hitch is Category '0' or Category '1' ? You need to be sure before shopping for implements. The Operator's Manual or a few simple measurements will tell you.
http://www.tractordata.com/articles/technical/threepoint.html
It is impossible to give you worthwhile advice on implements for the John Deere without knowing its stats.
I am a unsure about using a "Cultivator: on ground that has not been worked for years. "Cultivator" is a very elastic description here on T-B-N. Generally speaking, Cultivators are light implements.....and you have rocky soil. A "Cultivator" may work, or you may bend/break its components.