Here's the best I can tell you, from my 78 360 factory manifold. My 79 304 was near identical. The first picture is the rear, & the silver plate is the EGR, that I blocked off. Many of the stock things, you don't have. Big rubber hose from carb, goes down to the PVC valve. Next rear port is heater hose. Gold colored bolt & washer is plugging a vacuum port. Rear center top manifold is another vacuum port.
Second pic is front, center to right side. The front adapter unit is a manual water temp gauge. Next row back, gold bolt was probably the A/C Mount. I just plugged everything for cosmetics. Back across to the center, square gold plug, is a vacuum port.
The larger blue bolt between the vac port & therm housing is just plugged. It or the other one may have been used as a sensor for the emissions that came factory. If you remember or see pictures, they had vacuum houses, sensors, & tubes from the headers, like Spaghetti! If it's tapped all the way through, it would be in the water section.
Third picture is the driver side. I just showed this for the green wire/blue connector-clip-on, which is another water port. That's my electric water temp gauge. Most of the factory set-ups used this port.
