*a friend of mine* has tempted with the idea of SBR wk180 before.
As others said already wk180 takes AR barrel. Specifically you need a carbine length barrel with 0.750" gas block diameter. Mid-length will work too if you get the RWA gas piston.
Gas port size should not be a problem as the original wk180 is overgas'ed anyway. The gas port size on my MRA 18.6 barrel is smaller than the original barrel but cycles without problem.
The best way to do it is to get a spare upper to put your short barrel on. Then one can dance around the "inform within 30 days after changing to restricted" line and only swap on the SBR upper at the range.
Here's the parts list you need to build another upper other than the barrel:
Piston Gas Block UNIT: 50.00 QTY 1 50
Piston Cup UNIT: 15.50 QTY 1 15.5
Piston Sets crew UNIT: 1.50 QTY 1 1.5
Piston Rod, Carbin Length UNIT: 20.25 QTY 1 20.25
Piston Spring UNIT: 2.50 QTY 1 2.5
Gas Block Set screw UNIT: 1.50 QTY 1 1.5
Upper Receiver UNIT: 175.00 QTY 1 175
Barrel Nut, Low Profile, AR15 UNIT: 15.00 QTY 1 15
Handguard, 10" WK180 UNIT: 200.00 QTY 1 200
Bushing, Nylon, Piston UNIT: 1.25 QTY 1 1.25
Handguard Retaining Bolt UNIT: 1.50 QTY 8 12.00
Total $494.50