Airhead, look on the back drivers side of the block there will be a date cast into the block it will be a a flat screw driver type start and finish (they screwed this plate into the molds befor they cast the block)
it will have a letter then 3 numbers
the letter is the month
A = jan
B = feb
C= mar
and so forth
the next 2 numbers is the day and the last single number is the year which should be a 8 or a 9
original pontiac engines will have been manufactured within a month of the car
on the pass side front of the block it will have a 2 letter code stamped into the block
the 4 speed blocks are
WQ,WZ,WS,WZ,WT,WX
if it starts with a Y then its an automatic block
this will explain how to read the codes
http://www.gtoalley.com/engcodens.htmlif its an original 400 car it should also have a single or dual traction bar from the rear end just inside the leaf springs and goes to a stamped out bracket on the body .. (thats another way to tell if its a true 400 car) and if it is it could be worth alot
if ya get me the data off the plate in the engine compartment I can tell ya whats what with the car, emaul me with it if ya want