Mine is also a 9-69 build date 70 challenger.My suggestion would be to get the vin# and fender tag decoded first and see exactly what you have.If the car is an original 6 cylinder I might suggest keeping it a 6 cylinder car.Most of the 6 cylinder cars were used to swap a V-8 in years ago so finding an unconverted 6 cyl car is "rare".They also run pretty good and will get great gas mileage.I had an original '71 barracuda 6 cylinder years ago and wish I had kept it.They are alot more rare these days than a 'cuda with any other engine except the hemi.