Sounds like Amperex or GEB may be the best bet then. Perhaps a PQ, 7308 or one of the other classics? Both use 6dj8 variants and you will definitely want to swap out the other tube too (cheap and well-worth it to go NOS)...
Enjoy! If you want any really specific suggestions or notes, just ping me directly...
Jacob
Enjoy! If you want any really specific suggestions or notes, just ping me directly...
Jacob