There aren't many reputable shops in the area that have experience in subaru short/longblock assemblies.
Go read around in the built motor discussion. Best advice I can give you right now is pick a budget and power goal first.
What are you trying to do anyways?
Also, even though you aren't building the motor back to factory specs, the factory service manual does have important information that you'll need to know. Proper sequences to remove head bolts/case bolts, proper way to remove timing belt, torque specs, torque sequences, where to put sealant, etc.
There are also small things that you won't know until you run into them like SUPER tight cam gear bolts that sometimes need to be drilled out.