Go to the link below, it's for Pontiac Historical Services. They can give you from microfiche a copy of the actual factory to dealer invoice for the that lists all the options etc. Unfortunately you cannot tell if it's a real 400 car from the factory without running the VIN through PHS, unless the guy has some dealer or factory docs like the window sticker or broadcast sheet.
Production Numbers for 1967 was for a 2 door cpe (22337) 67,032 units , 2 door convertable( 22367) 15,528 units. Out of those 18,635 were 400's. I have owned two 69 TA's with RA III and a 67 400 as well as a 69 400 great cars that run hard and look great. But as you can see in 67 they made 18,000 cars there is most likely more then 100 left. If you are interested in the car you better run the VIN through PHS. The last 8 digits of the VIN number will be on a machined surface on the passenger side of the timing cover. The VIN will also be on the passenger side of the trans if it is a manual and on the drivers side above the pan right by the transmission shifter cable bracket on an automatic.
1967 400 engine codes for all Pontiacs
400 255 HP XL,XM
400 260 HP XB
400 265 HP WA,WB
400 265 HP YA,YB,YC,YD
400 290 HP XV,XU
400 293 HP XC
400 325 HP WU,WZ,WQ,WI
400 325 HP YE,YF,YT,XE,XN,XW,XX
400 333 HP WD,WE,WY,XT
400 335 HP WT,WW,YS
400 350 HP XZ,XY,XH,XJ
400 360 HP WS,WV,WR,XS,YZ,XP
The above engine codes are on the front passenger side of the block below the head. The 400 block casting number for 1967 is 9786133, this is by the distributer at the back of the block.
www.phs-online.com
Hope this helps