The "rattling noise" could very easily be a cracked flexplate (attached to the end of the crankshaft, which the torque converter, in turn, bolts to). Get the car up on a lift, start it up, and see if the sound isn't coming from right where the trans bolts to the engine. While replacing it will require pulling the trans, the flexplate is only a ~$30 part (new from Subaru). Make sure that the two alignment dowels are in place, as the lack of one - or both  - is a leading cause of cracked flexplates.
-Bill
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'92 Fully caged, 5 speed, waiting for its fully built EG33
'92 "Test Mule", 4:44 Auto, JDM 4:44 Rear Diff with Mech LSD, Tuned headers, Full one-off suspension
'92(?) Laguna, 6 spd and other stuff (still at OT's place)
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