Good day and welcome to the Forum! I have had my fair share of rebuilds and work with the ole' 8Ns! I simply love em! So let's see what we can do to help you here.
1st, bent 3point hitch. Doesn't sound good! You can often find parts for these tractors (there were over 500K made!) and lots of independent tractor salvage yards exist, as well as parts on Ebay and of course one of my personal favorites -
www.just8ns.com
I highly recommend Don Barkley (just8ns.com) for all of your 8N parts and info needs. His customer support, knowledge and professionalism is a credit to the entire tractoring industry in my humble opinion!
2nd, the lift faltering after 15mins is not that bad but not the best either. There are routinely 2 different weights of hydro/tranny (combined cavity for this beast) used --- straight wt. and new 134D Hydro fluid. The straight oil is heavier but you probably have a wear/tear issue with your hydraulic pump. Here is some helpful insight on how to diagnose that issue. You should first take off the right hand inspection plate under the seat on the side of the lift housing. With an implement on the lift start the engine and with the lift in the up position look inside and see if their is oil leaking from the end of the lift ram cylinder.If their is only a slight drip this is normal.If their is a fairly steady stream this may be the trouble.If the oil is coming from somewhere else try to pin point its orign. If you find no appreciable leaks on top in your view then you may have a pressure relief valve leaking. It is located just under the pto shaft on the vertical back of the pump. Sorta shaped like a spark plug and an 11/16" box end wrench fits it. You can check it for leakage by first finding it with the engine off and then with the pump running and with a load and hot put your finger over the end of the relief valve and if it is leaking enough to be a problem you will be able to feel the oil push your finger off the end of the valve slightly.You can check it by washing it up and then soaping it real good with some dishwashing detergent and water and apply air to the end that goes into the pump. If it is leaking you should replace it with a new one. Or just replace it if you have it out because these things are notorious for failing. The part # used to be 8N638
3rd, I use the 3 ribbed, but I have seen many people change to turf and even motorcycle tires for the fronts. I can get you more info if you need it on this conversion.
Lastly, it depends how much $ and time you want to put in it. Cost for good quality enamel paint and multiple coats can run you into some serious $$$ --- if you just want a decent restoration, you can of course tear the ole N down and sand, prime and paint each part. The time you put into it will help you in the long run as you will undoubtly find things to tighten up, repair and fix along the way with your paintjob!
?'s:
You didn't metion the year of the N, nor if it is side/front mount distributor, or anything else...How does the oil pressure hold up?
Have you done a compression check on the engine? Do you have a pictures?
I hope some of this helps! Welcome again!