A lot depends on what you need. Some things you can get by with aftermarket parts. However... In my experience in replacing seals, it's best to go with original Case/IH parts, unless things have changed in the last 10 years or so.
When I crossd reference to say a CR brand seal, I would end up mashing it. A couple times of that I went to IH. You could all but push them in with your fingers. Just needed a slight nudge with a hammer, and wooden block.
Again, it depends on what you are needing. Hoods, grills, gas tanks are pretty plentiful in salvage yards. Brake bands, clutches, gaskets, things like that you can get by with aftermarket.
Here is a link to Case/IH's parts website.
http://www1.caseih.com/northamerica/PartsService/Pages/search.aspx
You can go there, and find the part # for what you are needing. I usually have Google open in another window. I copy and paste the part number in the Google search engine. Most aftermarket parts dealers list their parts for replacing the original part number. So you can just shop for the best price with the results..
If you are looking for a used part, here is a link to Tractorhouse.
Used Tractors at TractorHouse.com: John Deere Tractors, used farm tractors and farm equipment, Case IH, New Holland, Agco, Caterpillar.
Look in the menu on the left, in red, for parts search. Click on it, and you can search by tractor model, or part number.
Those A's are great little tractors..!!
