johny, shouldn't be a problem to do. Locate the factory spot welds, clean the paint away from the spot welds with 3M clean-n-strip disc on a drill.
Special drill bits are made to cut spot welds, one type is a hole saw type, the other is a drill bit with a special center tip to help center the bit into the spot weld. The spot welds should only be cut throught the top panel. Then use an air hammer or small flat punch and hammer to break the panels apart./
today is much easyer than it use to be several kits are avalable for just that job in 67 we did a 65 mustang like that in order to put a 390 in it but we used the front end out of a van lot of work wint like stink on the drag strip but was scarey to turn good luck