Alright...
The International 340 came in several flavors, as it replaced the older International single digit and single letter tractors.
The International T6 / TD6 would be the predecessor to what the 340 is. The 340, however is also a wheeled tractor that shares the same engine. Much as the Farmall M, shares the same engine as the T6 and TD6.
Now, first you have to see if it's a T340, or a TD340 - the T is a gasoline engine, the TD340 would be a diesel engine.
Secondly, what year is it?
Third, you would really need to check the condition of the loader parts, who the loader is made by and the condition of the 'track' parts - i.e. final drives, pads, rollers, etc.
The issue with international crawlers (as I have 2 of them on my family's farm, and spent ALOT of time rebuilding each) is this - Engine parts are very, very easy to get. As well as certain other parts that were 'shared' between the tractor family and the crawler family. Transmission parts, engine parts, water pumps, etc. are all fairly available as long as you have a smart dealer that will cross it over. (When we redid the engine on the T6 5 years ago, we ordered all farmall M parts.)
The problems you run into, is everything else on the machine and the loader or blade package.
International made the engines and chassis, everything else was produced by aftermarket manufacturers. Every T series machine (T6 / T9 / T340 etc.) was sold as a 'tractor' first, then whatever you wanted to mount on it, you could. Unfortunately for us, the companies that made 'everything else' are gone. The majority of the IH loaders and dozers were made by 2 companies - Drott and Bucryus-Erie. My blade package on my T6, is a BE, which split companies, which half is gone and half is owned by CAT. Drott, is also nothing more then history - it became part of CASE.
My dad and I (meaning... I) replaced all the grousers on the T6 10-12 years ago. They were pretty much impossible to find, ended up having to have longer pads shipped in then cut down to fit, which gets very, very expensive.
Undercarriage parts are pretty much non-existent anymore unless you have access to a machine shop to make you new pieces.
So really, for $1500 - it depends on how much you want to spend fixing it up time wise and money wise. The engine, from what it sounds - gas or diesel - will need to be rebuilt. Putting new clutches in... is not fun. These machines are very cramped to work on and require a lot of heavy lifting to do.
If you do decide to restore it? Awesome. If not, I don't blame you.
The roll cage is more just like a 'brush' cage, then a roll cage on a track machine. It probably came with whoever made the loader.