Being a "Country " boy, I can translate for you. That expression would be the female version of "I'ld give my left nut for it.
In other words, it's a big compliment. Your car was so nice she'ld never be able to afford it without trading/selling a very important and highly personal body part!
You probably should have swung by her dads place. Hard telling what cool cars and parts we farmers have stashed in our barns and sheds.
She even said Dad was a big Ford man!
Fast Farmer