are you adding mechanical gauges or electric ones with senders?
i,m pretty sure for an olds (although i must confess i have only a little experience with the doggy smoggy 307 motors) takes it,s water temp from the front of the intake close to the t-stat,. see if there,s an extra plug that you can remove and put the water sensor in.forget the manual, it,s a look and see type thing, when dealing with olds motors in different cars they used different intakes, the oil pressure is real easy right at the front of the engine,.next to the oilfill tube,. just "tee" in where the factory idiot light has its sender,.
Nick