The true head casting is actually on the underside, reach out to other Longchamp owners to compare engine VIN (location, font, style)
EDIT ******* upon reflection and closer examination, you may have a 1972 LTD motor short VIN 2P*10541 with 1975 or 1985 heads. ******
I found a single reference to DT engine VIN. so will need another to confirm OE. Check your intake
The DT OE stamp should match your VIN plate