Hi Brett,
Without knowing your specific issues or disabilities i am just speaking in general terms here.
I know vehicles have been altered for hand controls and things of that nature for racers in different series. I think i even remember some write ups on this site.
You could potentially search the forums for threads on those types of vehicles and get in contact with the builders or owners to give you advice and have a better understanding of the specific issues you might face and what they did to help limit or improve those issues.
You might be able to send a pm to Joey D and ask him to direct you to the forum threads or members he knows that deal with disabilities if the search doesn't turn anything up.
If your that passionate about it I would say anything is possible but it is not something that is just going to happen over night.
Another idea you could possibly look at local series or even a smaller type grand prix type race where you would be closer to medical attention and not in quite so remote areas.
Maybe you could help prerun with a team to start off before you jump into a race car, lots of different ideas and avenues you can look into.
Plus remember there are a lot of ways you can enjoy racing and be a part of the action with out actually racing, maybe help put up course markers or take down after a race, relay radio communications, promote and run websites...most small series races are always looking for help with this type of stuff and will take all the help they can get.
Just some ideas, and good luck!