I am installing 540's and want to add water pressure and oil temp gauges. Where should I place the water pressure senders. Do they go in the T-stat housing, the water cross over in the intake manifold, or in the side of the block in a drain hole.

More than likely your water pressure gauge will be mechanical. You will have to run a small diameter (1/8") hose from the engine to the dash. I like to put the hose fittings in the top of the intake. This should prevent the hose from clogging with mud, sand or silt, like it would if you put it in the bottom of the block. You could also put it in the thermostat housing.
Eddie