I would just use the freshest cuts of good stuff you can buy, no guts. It won't take much to fill a blender full and your cost per oz should still be pretty low even though you are buying fresh shrimp, clams, etc.
I'm embarking on a mush-journey myself here pretty soon, gonna get it all together and make me some frozen food
I have been thinking about trying to procure some of those disposable plastic cube tray things that the store bought stuff coes in, wouldnt that be handy.
I'll do some digging on that.