are they made to the intake
Are you refering to the tube that bolts to the top of the stock muffler on one side, runs under the carb and back down into the other side? If so, that the heat riser (I believe that's the correct name) and yes, it is made onto the intake. It's purpose is to keep the bottom of the carborator warm and keep it from icing up by feeding hot exhaust gasses across it (exhaust moves from one side to the other . . . it does not mix into the intake). Many aftermarket exhaust do not have a provisions for this tube. It shouldn't hurt anything (other than looks) to leave it alone if it isn't used.
Heater Boxes have an exhaust tube inside with a heat exchanger outside. They bolt to the exhaust ports on the front (front of car) side of the engine and feed exhaust to stock muffler. Fresh air is blown from the fan shroud into the heat exchanger and into the car when you pull the lever to turn on the heat.
J-Tubes replace stock heater boxes and only have the inner exhaust tubes.
Heater Boxes or J-Tubes feed exhaust into the stock muffler which bolts to the rear (rear of the car) exhaust ports and the heat riser tube.
As Ret.Bugtech said, the Pea Shooters are the two chrome pipes that stick out the rear of the stock muffler.
A merged header replaces the stock muffler and (hopefully) equals out the pressure on all four exhaust ports. it ends in a flange that any number of aftermarket mufflers could bolt on to . . . none of them that I know of end with a pea shooter.
