Thanks Vas.
So here is one Tabiya of 5...Nc6 & 8...Bc5!? with 9...0-0  in the Halloween Gambit:



White has several options here : 

* 10. Ne4 Re8 11. Bd3 Qxf6 12.Qe2 Qd8 is interesting
* 10. Na4 Re8+ 11. Be2 d6 12. Nxc5 (12. f5) 12... dxc5)
* 10. fxg7 Re8+ 11. Be2 d6 seems bad for white
* 10. Qh5 is playable

There is also 9...Qxf6 that is interesting:





So maybe this 8...Bc5 variation is not strong enough to be called solely the best variation versus the Halloween Gambit.

I actually guess now that this line is the most annoying for white:

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Nxe5 Nxe5 5. d4 Nc6 6. d5 Ne5 7. f4 Ng6 8. e5
Bb4 !



White has to take the knight on f6 and here black 9...Qxf6 seems best.



PANFR: 10.Na4 Re8+ is good as it allows ...Bg4 in some lines. Moreover is there is no Bishop in c5 later(Na4 played), then Kf2 is possible instead of the pinned Be2.

I've played almost 40 games online (blitz/ bullet) with 7...Bd6 with a nice plusscore. White is surely fighting for equality.

While looking at the Halloween Gambit, I was not 100% satisfied with "official refutations" available, until I found out this particular variation:

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Nxe5 Nxe5 5. d4 Nc6 6. d5 Ne5 7. f4 Ng6 8. e5
Bc5!



Then follows:

9. exf6 O-O 10. fxg7 Re8+ 11. Be2 (11. Ne2 Qh4+ 12. g3 Qh5) 11... d6



This line is quite forcing and after 11 moves black is better with the attack.
I strongly believe in this variation and would be pleased to have your feedback on it.