We are adding to an existing floor that has 1 1/2" wide, 3/8" thick tongue and groove oak (white, I think) strip flooring. We would like to match that floor and continue it in the new space, but having trouble tracking down suppliers who carry the 3/8" thickness. The project is in Houston, TX.

We found a supplier out of Florida (flooring.org) who shows inventory in the correct dimensions, but we don't know anything about their reputation. If anyone has used them before and can provide a reference that would be welcome.

We would be glad for suggestions of other distributors/mills to check with for this material. Thanks!

Are they members of the National Wood Floor Association? That would be good enough for me. They have grading rules for defects, milling, and average lengths.
Select grade is very good, but to get all heart you can specify clear grade which doesn't have sap wood streaks. Try to match the grade you have.

Pete, thanks for the reply. Good thought regarding NWFA membership - I will confirm. Point taken regarding matching the grade in addition to species.