Thanks again Kim!
My boy and I both like a tach up on the dash but the matching one to our gauges only came in a 3 1/8" OD. There's only one dash mount cup made for that size tach and it's plastic and expensive.
Soooo, we had a local exhaust shop stretch a section of 3" tubing out to 3 1/8" ID...nice, slight, press fit for the tach.
We pie cut the back side of the tubing, hammered it into shape over a ball hitch, welded it up, and smoothed it a bit.