Differences between 70/71 and 72 Darts

Will 70 dart fender bolt up to 72 dart fender extensions?
Yes they will

The hoods are generally the same and interchange, but the adjusting system at the hood hinges is different - you can use a 72 hood on a 70-1 car and visa versa, but you have to use the hood hinges for the hood you are using - 70-1 hinges on 70-1 hoods and 72 hinges on 72 hoods.