Do you have any contracts from GC's in the past you could "cut and paste" to make your own template? Something you could cobble together then have your lawyer draw it up. I've found my legal bills are less if I do the basic legwork upfront.
The basics to cover -
The obvious - Project location, owner, parties to said contract (GC - sub), date of contract, contract amount and scope of work (well defined)
Next would be insurance requirements, schedule including start date, duration and finish date.
Then what happens when the sub defaults and how that is handled. Best to have your lawyer write this in order to make it legally binding in AL.
Arbitration clause.
Other things to consider -
Indemnity agreements which can get tricky so I would suggest a lawyer for that as it overlaps with insurance requirements and riders.
Employee requirements such as must have a qualified supervisor on site that can make binding decisions. Recently I've seen a requirement for this individual to be fluent in English.
I've missed a few items but this is a good place to start.