The old way it was done was to use adapters in the intake manifold. IMO, this was ugly, but the only way it could be done. On a Chevy engine, it is on the side of the engine into the block, out of the way and neat looking.
Most chevy small block water necks/thermostat housings also have a port in them for a mechanical gauge. which ironically enough will fit some small block and big block mopars.