tpi manifold wont fit on afr heads any help???

hey guys iam having a problem with a 383 sbc my boss built then passed to me to finish i got the vehicle running with a painless harness but had a bad oil leak from the block to manifold area when i tore it apart i found about a 3/8 inch gap(huge) between the block(front and rear edges)and the intake when it sits down on the heads, iam using a big mouth tpi aftermarket intake with there runners the cylinder heads are airflow research #1119 i havent been able to find info on the heads but any help on what causes the intake to sit up too high (mismatch combination) was mainly wondering if anyone has run into this problem building a tpi motor.....  thanks for any help  

Are the heads milled?