you sure its got a vga in ?
if so that is so cool and you are lucky
since the 7" touch screen is measured across the diagonal
and the 6.5" is also the difference is small and as long as your are careful on how you mount it so it doesnt catch between the screen and plastic moulding it shouldnt be a biggie
if you google there are 6.5" touch screen elements out there
I would suggest as a first step to strip the dash and see how big the touch screen element can be, then go from there