conversions can go one of 2 ways, and they generally go this way, like mine did:
Find a suitable bike in your size after months of scouring CL/ebay, that is rideable out of the gate.
spend too much money on powdercoating.
Hunt for a few more weeks enlessly searching for parts to make your bike the way you want it.
find out that some of the parts are not compatible with one another,
Keep looking for parts.
Put together, only to find that something is not quite right.
ruin at least one part in the process
go to LBS, and get assistance, and purchase additional parts.
Ride.
Now my lbs is a dream, ss/FG specific shop with a really talented mechanic/owner, who is seriously a nice guy. YMMV.
I ended up with almost exactly what I wanted, but I easily spent as much as an off the rack bike, and well above what the Bikes direct bikes run. And I do not have very high end parts on it, as I tried to keep the cost down.