Anyone know how to hook up an o2 sensor on a modified carbed 502,running way too rich,75 and 80 jets in a 950 holley.Ran great with K.eickert exhausts but too rich for my Gil's. How do you install it upstream of the cooling water?Dont want to waste time with trial and error jet swapping and plug reading.And does anyone have a ratio meter for sale...thanks Frank.

Put the bung in the riser just above the joint where the manifold meets the riser. Drill a hole in the riser for the bung to fit in. Then weld up the gap between the inner and outer pipe. You may have to squeeze the two pipes together. I put the round part of a ball pein hammer on the top pipe and then hit it with a hammer to cave in the outer pipe just a little to close the gap. You can then weld the gap. After the gap is welded, then you can weld the bung in. This way, you have closed off the water and don't have to worry about the bung leaking. Good luck.
Eddie

950cfm is too big of a carb for a 502 and contributing to the problem. If it was just an exhaust change, then you really shouldn't have to change more than a couple jet sizes.