29 Hudson heat riser tube

Unknown

My son Paul and I are about to replace the intake tube in the heat riser and have a question. Geoff says in a much earlier post that it is "easily replaced" We have a piece of 1.625 od tube. The top hole in the cast iron piece measures 1.620 after cleaning. The bottom hole appears to measure 1.600. If anyone is checking this site who has done this repair does the tube have to have a step machined into it to seat into the bottom. We can do this but would like to hear from Geoff or someone else who has done this before. I am also a bit reluctant to press the tube in if it has a .005" interference. sure do not want to wreck out last casting.

Thanks

Karl