Early fox body dual exhaust conversion questions

Since no one else has jumped in, let’s chat. What does your car have for manifolds? Can you share pics of the manifolds?

I think my 79 had cast iron exhaust manifolds, and I updated them to E-7 (87) factory headers when I switched to to dual exhaust. I had a talented old exhaust guy run duals “for off-road use” without the double hump crossover. I planned on switching, but he ran the other pipe without it hitting or hanging down in the way.

For what I am thinking about for you, pictures from the top will be better. I am interested in the heat riser since it also seems to be a concern. A good exhaust shop can make the dials (edit : duals) you need if the headers are a different length.The cost of a custom system with a H pipe was not worth trying to hassle fitting pre bent Walker exhaust pipes myself.

I am trying to remember what I did on my 79 to make the combo close to stock looking and functional. (I refuse to admit the number of decades involved.)
Is the heat riser a stamped steel box that connects to the manifold bolts and the flex tube that goes up to the bottom of one filter snorkel on the 83 GT? Right before I switched to dual exhaust, I also went with an Edelbrock 4bbl intake, the 4bbl EGR spacer, a Holley 1850-2, and the GT dual snorkel filter housing, including the fender CAI bellows and inner fender connectors. I do not remember if the “heat box” was From the 79 or later GT.
So I basically had the same top equipment, eventually on an E-7 roller cam, long block. (Not so fast now, but pretty zippy at the time with posi in the 7.5” diff.)
I know I bought the flex hose for a heat riser and had it attached to something on the exhaust. I do remember not much trimming or fabrication, some VHT paint, and no big problem.
I am sure I swapped the upper intake before the exhaust, so the heat riser box worked with the 79 and 87 exhaust without any big hassle (for someone handy with tin snips and duct work type sheet metal.)
I hope this gives you ideas. I do not think you have to keep your stock exhaust to have your car warm up on cold mornings, but a pic of the heat riser you are talking about would sure help.