Who makes couplers to connect 2 v8 engines together?

There isn't a single company that specializes in making couplers to connect two V8 engines together. This is because such a setup is extremely rare and usually a highly customized, one-off project for specific applications (like extremely high-power vehicles or niche industrial uses).

Someone wanting to do this would likely need to:

* Design a custom coupler: This would require engineering expertise to account for the torque, vibration, and alignment challenges.

* Source custom fabrication: A machine shop specializing in high-precision metalworking would be needed to manufacture the coupler based on the design.

In short, there's no "off-the-shelf" solution. The process involves custom engineering and fabrication rather than purchasing a pre-made part.