That didn’t take long to resume the journey!
I ordered a 12AU7 9 pin to 6SL7 8 pin tube adapter from: Deyan | Headphone Reviews and Discussion - Head-Fi.org.
As for input tubes, it really depends on your sonic preferences per @PaisleyUnderground. I generally prefer to use tubes that are not warm with my Mogwai SE. I picked up a 1970s Tungsram Czechoslovakia made from Brent J that I’m quite happy with ($40) – Telefunken like sound signature.