I want to make an extension to my dining room table, approximately3' x
4'. I want to match the color, stain, and edge to the existing table.
it will bolt on to the existing metal table frame on one side with two
bolts, and have one leg set on center about 18" in from the edge. I
anticipate using 1x4 about 4" in from edge (approx) to match existing to
beef it up and keep if from torquing.

What would be a very good furniture grade 3/4" plywood to buy for this
project? Going to rout the edge to round with the little edge on there.

Birch core with veneer?

Any suggestions, caveats, or tips appreciated.

TIA

Steve