Engine possible oil leak in order of most commun:

-Oil pressurer senders, mostly the one between pushrods, left side, 2 left
gren arrow, i never saw an high pressure leak!
http://www.benplace.com/syncro/syncro61.jpg

-Bore hole plug, right, upper yellow arrow and lower, the upper one ALWAYS
leak to some point.
http://www.benplace.com/head3/100_0025.jpg
(on this pictures, you see all possible leak)

-Rear Crankshaft seal (red right arrow)
http://www.benplace.com/bjp_head2/100_0008.jpg
http://www.benplace.com/bjp_head2/100_0011.jpg

-Oil cooler O-ring (left botom)
http://www.benplace.com/gilles/gilles6.jpg

-Oil filler neck (follow the tube where you put oil)

-Dip stick hole

-Oil pump sealing nuts (green arrow on second picture)

-Oil pressure relief valve (well, it's obvious when it leak)

-Pushrod tube (remove both tins, obvious)

-Cracked case

Yea, clean it with brake cleaner, take picture of leak, posted here, you
will have your answer!

Cheers, ben