40k miles is not what I would consider a "new" engine... I think your getting close to thinking about timing belt..
(Note: I am not a mechanic... lol.. and not 100% sure of duty cycles on Supras... just learning still
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It could be your front seal quite easily. I dont think I have put a new engine yet that hasn't had at least one issue.. either due to some monkey doing something funny when building it (all of us are fallable) or a part not being made quite to what spec it should be. My advice is to do 2 things. First.. clean off the engine where you suspect the engine leakes from and secondly, park it on a piece of cardboard. (I mark my tire positions on the cardboard so I can measure how far to the area if I am having trouble finding the exact spot) Bear in mind.. oil travels... and you may have to drive it to get it to leak, so the drip might be from when your driving and its being pushed backwards from the real leak area or travelling along a hose or the motor or what-have-you...
Thats my "amateur" suggestion.