This is getting confusing. What is your brother using for an engine in the 70 Duster?
If he is using the trans that was behind your engine, and his engine is 1968 or later, he will have the opposite problem. The hole in the crank will be larger then the snout on the converter, and the converter will not be supported. If you have his converter, what is he using for a converter? If he has no engine in the Duster, get the trans from the duster (that was behind the engine you just put in your car), and use that trans, and the red converter.
