If he can spend the money to switch engines why not use that money to just trade for a skid steer that has what he needs on it???
That L35 is an older skid steer, 1976-1982. It also was the smallest New Holland made at that time. It sounds like he is going to try to get a business started with it. He would be better off to have a better machine even if he had a payment. He would have something that would be much more reliable to use and keep working.
Used skid steers are a dime a dozen around here right now. Everyone wants a new one but almost no one wants a higher houred used one. The term higher hours is about anything over 2000 hours here. Just about every dealer has a lot full of used machine right now.