I'm trying to simulate a specific ram chip, but it uses bidirectional data pins. So far as I can tell there are input and output pins, but no way to combine them.

You can use two Buffer gates and a NOT gate to create a 1-bit bi-directional buffer gate.

See the datasheet for a 74HC245 (8-bit transceiver) IC for more details.

I've tried using the strategy in the 74HC245 datasheet it didn't work, it throws "Contention error 0 and 1" still. Making it impossible to build the circuit I wanted :(

Sorry, we don't support bidirectional pins at the moment. Because of the way buffer elements are resolved in the circuit, it is not possible to create a bi-directional buffer gate either.