Here is the specs for the motor that came with the car.

Block:
Unit Number - 470117
Type Code - ZX (1972, 400CID, 200HP, 4BBL
VIN Code - 22C321409
Casting Code - 481988 (1971)

Heads: 7 J 2
1972, 400 CID, D-PORT, Intake valve 1.96,
Exhaust valve 1.77(odd), Chamber volume 96CC

Here you can see the codes I got off the block.