Hi ReJ
Your questions seems a bit unspecific...
If you want it movie accurate, do NOT deviate and use all the parts the prop dept. used as well, if possible.
If you just want to build "a" blaster, based on the design you chose, feel free to incorporate whatever changes you want/ need to make the build happen.
Are you trying to make it part of a costume and go for approval? What are the regulations of the specific group you´re trying to join?...