I don't know of any smiths, but I've built one and have another in the works.
Is it built up right now or are you putting it together from parts? If you bought it complete it should have all the necessary US parts. IIRC you need 7 US parts to make the FAL compliant.
One mine it was:
Receiver
buttstock
pistol grip
hammer
trigger
sear
charging handle
Here's teh list
Section 922(r) of the Gun Control Act (GCA) prohibits assembly of
certain semiautomatic rifles and shotguns from imported parts. The
implementing regulations in section 178.39 of Title 27, Code of
Federal Regulations provide that no person shall assemble a
semiautomatic rifle or any shotgun using more than 10 of the
following imported parts if the assembled firearm is prohibited
from importation under section 925(d)(3) of the GCA as not being
particularly suitable for or readily adaptable to sporting
purposes:
(1) Frames, receivers, receiver castings, forgings
or stampings
(2) Barrels
(3) Barrel extensions
(4) Mounting blocks (trunnions)
(5) Muzzle attachments
(6) Bolts
(7) Bolt carriers
(8) Operating rods
(9) Gas pistons
(10) Trigger housings
(11) Triggers
(12) Hammers
(13) Sears
(14) Disconnectors
(15) Buttstocks
(16) Pistol grips
(17) Forearms, handguards
(18) Magazine bodies
(19) Followers
(20) Floorplates
The FAL has 17 of the 20, so you need to have 7 US parts to bring the count under 10 imported.
As far as headspace I have a set of .308 headspace gages and some gage pins also to check the headspacing, depending if it's built or not.
Hope it helps.