You could set that up with a custom part if it's something you don't place often.
If you plan to use these over and over again, I'd recommend setting up a new part in the catalog and adding it to your spec.
In this image below, I've added standard 4" flange blind to the model, then exploded it. I convert that to a standard AutoCAD block. Then used "PLANTPARTCONVERT" command to add ports on each side of the flange.
Next you want to setup the custom part. Click the "Custom Part" button up on the ribbon bar. When the custom part window comes up click "Choose block from model". Select your block and configure all the properties and port properties:
The main property you need to fill in is "Long Description", what ever you type in there will come out on the BoM on the Iso drawing.
Port "S1" will be FL for flanged and in your case, 5" nominal diameter with matching pipe OD of 5.5625" (I used a 4" in this example)
Port "S2" will be 3" nominal diameter, matching pipe OD of 3.5", endtype "TAP"
Once you click "insert part" it will allow you to place the flange blind in the model. You can place it right up against plain end pipe and it should thrown in a weld neck flange. The little exclamation point shows that it's a custom part and not a spec part.
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