Joe B, If i understand your your question correctly, I am building a 8ba engine that will be put into a case ingersol garden tractor, with the tin work of an B allis chalmers tractor, there is a guy in northern wisc that built one of these tractor, he was very generous to help me with the plans on doing this project, anyway I had a carb builder from texas bulid me a 3x2 intake with stromberg 97s and what he did was machine in a tap into the passage of the casting leading to the draft tube and that tap will be used to recirculate the PVC gases, and the road draft tube I will find something like a solid rubber ball or something like that and jam it into the draft tube to make the tube non function, and still keep the look of the tube intact, I hope I was able to answer the question, I wish i could install pictures on the site and I have tried in the past and I failed, Hope this make sense