BERNIE - I agree with Greg, hard to tell if hyd hoses are bad until the engine is running and pumping oil. There is steel wire braid inside those hoses, that's where their strength comes from, the rubber covering means very little.
The rear main seal on my Super H has dripped oil for 50 years, and it's only 67 yrs old. When I overhaul the engine it will get fixed. The clutch could be O-K, once again, hard to say without engine running. Dad had a FARMALL Super M-TA and a FARMALL 450, both had TA, you push clutch in, still can't pull trans out of gear, pull TA lever back into the low side, transmission slips right out of gear. HAVE THE OWNER'S MANUAL IN HAND when you adjust both clutch and TA. In my opinion, pretty good chance the clutch is fine, the '51 FARMALL M out in my shop still has the factory installed clutch in it and it was Dad's loader tractor since it was brand new. IH used ROCKFORD clutches, they're TOUGH.
The 350 utility has disc brakes, but WAY different than car or truck disc brakes, it has two discs with an expander between them inside a cast iron housing, friction material on both sides of the discs, and a machined & polished iron friction surface on the inside of the cast iron cover, the a friction disc, then two expander plates held together with springs, another friction plate, and the last machined and polished cast iron friction surface. The cover is only held on with 5 capscrews, loosen the adjusting bolt completely and remove it, then the entire cover. Inspect everything. There's three 1 inch diameter ball bearings between the expander plates, make sure the balls are smooth and round, make sure the grooves they roll in are smooth, and upon assembly coat the grooves with a kinda thick coat of anti-sieze, about 1/8 inch is fine. New balls are rather cheap. The 3 coil springs around the expander need to be strong, they were $12 each last time I bought them. Set of four friction disks were $64, $16 per disc.
There's three good sources for wire harnesses, Brillman, Porch, and Ag Services, they probably have your replacement switch too. The ignition points and condensors sold today are all imported, and are crap. I have read on-line that Standard Automotive still makes conventional ignition parts that are probably as good as you will find. The points, condensor, and spark plugs in my 1954 FARMALL SUPER H, the next model older than this 300, I bought and installed sometime in the 1980's. I hadn't run it since last June or July, but if I had remembered to turn the gas on, it would have started and ran on the second revolution last Saturday. Back then I could still get genuine International Havester parts. You can probably still buy parts from a Case/IH/New Holland dealer, but hard telling where they were made. But I'd trust them more than a lot of the junk offered for sale other places.