I have a Woods 750 that I bought in 1991. It is now the 7500. It uses heavier buckets and has some other minor changes. I use it on a Ford 3000. That is 1000 lb heavier than an 8N, with 10 more hp. It seems like a good match.
Do not think I would use it on my 8N. For one thing, it will not mount to the 8N top link rocker. I had to replace the top link rocker on my 3000 after the back hoe broke it. The cast iron top link rocker is just not strong enough. You probably don't know this, but the whole back hoe hangs on the top link rocker. The lift arms do not hold any of the weight, they just stabilize the hoe.
The reason for this, is that Woods has a patented frame on the hoe that keeps the hoe from lifting up under load. This is a safety issue. If the hoe could lift up under load, it would push the operator into the tractor, RPOS or steering wheel/dash, with nasty results.
I think that the 6500 might be OK on an 8N. Would want to check the weight. I have the 750 weight written on my manual - out in country, so can't get it for you until this weekend. You would need to find a way to attach it to the tractor, other than the original top link rocker. I suspect that Woods does not have a replacement for the 8N rocker like they do for the 3000. Even if they did, GOOD LUCK on getting the old rocker off. After I broke mine, it took heating the begebers out of the rear axle mount and a 10 ton hydro. jack to get the pin holding the rocker to the axle housing to come out. WHEW!!
I would look at using the "ears" on each side of the 8N rear axle housing. I would want the Woods engineers to approve any change in the Woods mounting bracket. SAFETY First!! I do not think it would be very hard to design an acceptable bracket, so it should not be a big deal for Woods to do it.
I winced when I paid the bill for my NEW 750. But I sure am GLAD I have it. It is a great tool for using around my farm. I've dug a 300' trench to replace an old iron well line with new PVC plastic. Dug for culverts across the logging road into my woods. Dug out stumps and even trees up to about 10" across. Dug out some BIG rocks in my hay field. And several other tasks that either would not have been done or would have been MUCH harder to do. Not sure it has yet paid for itself interms of cost per hour for a rental unit with operator. BUT it is there when "I" need it so I don't have to call someone, wait for them to get free from their current job, etc., etc., etc. :-)
If you get a Woods unit, let me know. I can give you some pointers on mounting/unmounting it. It is not as easy as other three point hitch implements. That is because you have to work with a FIXED relationship between the lift arm pins and top link pin - top link does NOT adjust like you can do on, say, your mower.