can you feel my heart?
Bulky Ghosts don't bother Conkeldurr as long has he's got +1 or +2 under his belt already. The Will-o-Wisp they give him just further increases his damage output because of Guts, and Payback smashes every Ghost-type out there. The only precaution I'd have is a Jellicent who can get in on a +0 Roob and Taunt it to prevent it from Bulk Up'ing and Cohag, who if you Payback prematurely (a +2 boost with Guts burn OHKOs it iirc) will give you Mummy and you'll have your attack devastated by the burn. I can't remember if Mummy works when you KO it but I don't think it does.
I'd much rather use Conkeldurr, tbh. :) (psst also no bulky ghosts use t-wave iirc - at least, not the common ones)