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It sounds like you can get approval based on the large down payment you have for the vehicle. The issue will be the interest rate.
IMO it would be best for you to go to a credit union for approval rather than trying with the dealership. I am certain the dealer finance office will shop your application out to many lenders and you will end up with a subprime lender (based on your score alone). With a CU you can mitigate risk by having the large down payment and you don't have to end up with one of the subprime lenders.
But, before you do that, have you visited the rebuilding forum here? I bet you can get your score up quickly before you purchase the truck of your dreams. Specifically take a look at this thread: http://ficoforums.myfico.com/t5/Bankruptcy/HOW-TO-From-BK7-discharge-to-700-in-24-months-or-less/td-...
Have you added any new cc's since your discharge 5 years ago? If not, that is why your score is low. You need revolving accounts to bring your score up - you don't need to use them except once in a while, but you do need open, active TL's.
Not neccessarily, depending upon the CU. They don't only look at your scores but what is your relationship with the CU. Some CU's won't finance you for a car until at least 12 months after BK while others as early as a month after BK. It is all dependent upon what their guidelines regarding loans and BK are. Can't hurt to ask, you maybe pleasantly surprised your CU can do a better deal then the car dealer.
Why not app jointly so you get the benefit of her score and your income?
If you're putting 80% down on an expensive vehicle, just about anyone will finance you, as it's secured and if they repo they win a lot of money.
I think you should hit the rebuilder forum to find out why your credit score is still so low. You'd be surprised how quickly you can raise up 100 points when you're that low, especially if you have the money to deal with collections or to get secured credit cards and the like.