Pardon the clutter on the floor there.
First we must open both blasters and take out the internals. The blastzooka is difficult to get all the way apart but you can just pull out the whole tank piece from the back. Of the raider parts, you will need to use for this mod the barrel, jam door, barrel stabilizers, trigger and spring, and the back stock capping piece.
(Insert image here)
Cut the entire stock orange barrel of the blastzooka off. This can be done with a dremel, saw, or pipecutter. Be careful not to get any shavings inside the tank.
Next, Dremel or drill out the back end of the stock attachment piece. This will be where the pump goes through. On a side note, this blaster works best with a retaliator stock due to the way the stock is open on the back, see the first picture for reference.
Before we get onto actual shell modification, take off the jamdoor lock, pictured below as the square orange piece on the bottom rail. I only had to unscrew the bottom right screw to take it out. This will allow room for the tank and will let us open and close to jam door at will.
Next we will need to dremel or carefully cut out a section of the blaster where the blast button needs to go. In the picture below where there is a bunch of hot glue to the left of the button is what has to be cut down. Cut enough to seat the tank properly and have the shell fit together over it. Test where the button must line up with your trigger and spring. For my blaster I had to add extension pieces to the trigger so it would depress the blast button fully. I used two pieces of the blastzooka shells trigger button for this. I cut them into squares and superglued them in place. Any adhesive would probably work though.
For the next step, make sure your tank is seated well and you can fire it by using the trigger to depress the blast button. Once you are happy with that, its on the the barrel section. You will need a 1/2 inch PVC coupler. Cut it just behind the middle as pictured below. I apologize for the bad focus. Our breach section dimensions are 1/2" for either end, and 2" for the middle where you dremel out the actual breach. After you finish this you will need some "magic cpvc" that fits and slides inside your 1/2" pvc without issue.
Once you have completed cutting out your breech, stick your cut coupler onto the nub end of your tank. My piece friction fit on so I did not end up gluing it, but you may do so for a better seal. Seat your PVC breech inside the end of the coupler and test your CPVC by placing the tank back and measuring how much you will need to get a hand length from the front of the barrel. Cut it to a good length. I would advise picking a length of CPVC that both fits inside your PVC and has a looser fit on your darts.
You're almost done. At this point you can decide if you want to load the blaster from the right side like mine or the left side. If you choose the left side take your shell and take off the raider mag-well, it is screwed in place. I will probably adapt mine to this way later. The last step you need to take is to line up and cut the blasters barrel guide piece so it fits well with your breech. This is crucial so your CPVC will guide into the breach properly. The cutting here is mostly by eyeballing it. Do your best.
Once your pieces all fit together properly, you only need to seat your tank so it wont move inside the shell. I hot glued the tank in place because I had no epoxy available but I suspect epoxy will be the best choice to use here. Anyways, adhere the tank to the shell, making sure your trigger is properly set so it works. This needs to be stable so that when you pump you don't break the adhesive and make the tank come loose.
(insert picture here)
Close the blaster back up and screw it all back in place. If you dislike the pump coming out of the back, fit an endcap piece to it and dremel a hole to fit the pump. I left my pump unplugged because at the 6 pump max it is occasionally exploding stock elites.
