Don't worry so much about the lifting capacity of a loader, that will be what it will be once the loader is installed. What I'm trying to say here is if you go by the lift ratings of a particular loader, and you have a higher or lower hydraulic pressure on your pump than the factory ratings on the loader, then all those ratings will be somewhat different anyway.
I would focus more on getting one that fits and mounts correctly, and then worry about its' capabilities afterwards.
If your friend is looking at a new one, then he needs to purchase the mounting masts that were designed for his tractor. That *should* make an installation go much smoother.
Two other things to consider..... It's likely your friend will need to ballast the rear tires, and/or use a weight box for optimum (and safe) operation. Also, if his tractor doesn't have power steering, that could make steering difficult with a bucket full of material. This could be a pain if/when doing serious loader work that involves lots of short backwards and forwards movements with a lot of turning involved.
