conversion kits and all that are always trouble to the newbie rider.
i know you don't want to hear this.. but you could probably just buy a 27"fixed wheel with a cog and lockring on it if you check all your lbs for only like 70.
i found one a year ago.. and i know my lbs said they could just order them if there not in stock.
saves you a lot of work, plus it's much lighter and safer that an old converted wheel/hub.