Where to start on rebuild

[Dirtydev]

Hello new to this site see if I can get some help I recently got my blasters back from a scum bag who was supposed to do a rebuild on the one and use what ever parts off the other and ened up making them worse then when I brought them to him and tried taking them and my money I won the court case and got them and my money back but I do not know where to start or even see what parts I need what's missing and what is not I got a bins of parts these are the pictures I have as of right now any help would be appreciated I can upload more pictures as I dig into them

 

[Larry's Shee]

I would start with closely inspecting the frames for bends/straightness.

Then organize the rest of the parts to choose the best..

As to the engine DO NOT buy Chinese parts of any kind !!!

 

[Dirtydev]

What would you recommend for a piston brand like wiseco is there other decent brands