Intercoolers come in every shape, size and configuration imaginable. Likewise the inlets & outlets. If you can find an engine like your own that has one, it would be a good place to start. If not, generally, bigger is better. The only real possible downside is an arrangement that creates too much pressure drop across the system. Check with any of the actual IC manufacturers as they can provide specs for just about any engine.
NOTE: Most of what you see online are retailers...not builders.