Subaru powered OFFROAD project

I am building a OFFROAD vehicle using a 83 Subaru 4X4 GL for the Engine/Trans/Drive train... I have the engine installed in new frame but the engine will surge (rev'ing between 1000 - 3000 rpm's) when I try to idle. Though it was an air leak at the base of the carb. Reinstalled the carb with clean gaskets and gasket sealer. NO CHANGE. Any ideas or suggestions as to other items to check that may be causing this conditon. Note* I am using the original wiring harness form the donor vehicle.