I have one of those blocks in my pelt
chiller (with 1/2 lines+fittings). The channels are soooooooo restrictive that the 1/2 fittings and lines are a joke. (if it has 3/8 just leave them)
I assume you were planning on using three blocks+2 pelts?
Why not do this........
take both maze lls and remove the tops, get a 1/8 sheet of copper and cut a rectangle the size of the maze, drill a hole in the center to line up with the center 'port'. Solder the blocks together with the thin p;ate in place. Drill one block on the side to accept a brass fitting and do the same with the other...tap them and screw in the fittings. then get two other blocks and make a sandwich with the modded mazlls in the center.
A lot of work but the double thickness and the amount of time the water will be being 'chilled' should really help cool things down.
wj