You're pulling it apart anyway, but my idea is this (probably belongs in 92-99, but we'll go with it for now.....if it works, I'll do a Techinfo, as this is the only fairly common leak on high mileage 3800'*):
Because this isn't a pressure leak, and only oil being splashed around under the lower intake by the valvetrain, it might be easy to 'patch'.
1. Clean the engine thoroughly with a commercial product like gunk foamy engine brite.
2. SCRUB the area in question (where the lower intake, heads, and block meet in the corners) with a nylon brush and degreaser. Rinse well.
3. Start the engine, run for 5 minutes to evaporate the water. After 30 minutes of cooling, wipe the area with an alcohol soaked rag to make sure you got all the oil residue.
4. Patch the area with hi-temp RTV sealant. Since this isn't a pressure leak, it should hold.