You're going to easily hit the field limits with a count of 600 so another strategy will be required I think.
Take a look at the Help file, Appendix A - Technical Specifications.
You may hit some other limits too - number of characters for example.
With those limits in mind is there any evident way that you could see to split your 600 field records or pre-select the fields you need and perhaps generate a new file that comes in under the limits?
You have the Monarch Utility to assess, notably the part of it that deals with file preparation to get things ready for Monarch when files are large, etc.
There are also other utilities out there that might be able to help if Monarch utility is unhappy with 600 fields or the length of the lines. It has been a while since I needed to use it and I can't recall if it has any limitations that might affect your requirements..
It would be unusually challenging to deal with 600 fields for a single reporting requirement, though perhaps not for an ETL application.
If you are able to split the file and then treat the separate parts as individual databases (or reports maybe) you should be able to create a resulting data set that will be within the limits. You might need more than one set. Indeed depending on the purpose several small sets might make for more flexible later re-combining activity.
If you need to go down anything like the Split and recombine route remember that you will need to allow for the creation of keys with which the re-linking can be achieved. I'm sure you know that but I always think it is worth a reminder.
Thanks for the input Grant. I explored the additional sources you mentioned and everything confirms that I am dealing with limitations. Other options of splitting and recombining or receiving the data in multiple files are valid, but then I have to think about what is practical. Going back to the vendor at this point to request another iteration of the file with fewer fields.