Russell,
The I.D. of 2 in. pipe is 2.067 in., the O.D. of 1 1/2 in. pipe is 1.9 in.that gives me 0.167 in. It will be tight but it will work, I have done it before. I will plug weld the joint to keep it there.
On the base I will use 2 - 1/2 in. grade 8 bolts through welded in sleeves in the...