^^^ Yeah that's a common leak point on RX-7's as well and all my transmissions had a leak there of some degree. Assuming the Miata bearing cover is similar to the RX-7 there's just a (very) thin paper gasket between it and the bell housing. Be sure to keep track of those shims! Also, let me know if you need any Miata transmission stuff. I still have the bell, intermediate, and tail housings and some misc. front end stuff (shims, bearing cover, etc.) from when I swapped Miata gears into my RX-7 transmission.