67 Barracuda Big Block K frame keep it or change it ??

Original big block car i wouldent cut up. Thats what slant 6 and 318 cars are for. My 67 was a slanty, going to be a 408. My sons 69 was a 318, but we are going to build it his way. No pedigree in either like a factory BB car has.

and if it's a numbers matching big block please keep the original drive line with the car unmolested