I saw this on a Hot Rod forum:

The spacers will make the intake fit,but will raise it up so high that the distributor wont work.You have 2 choices on how to fix that.One is to buy an aftermarket distributor with an adjustable collar,and the other is to mill the distributor boss down on you intake manifold to correct the differance.Bolt the intake down with the spacers and gaskets,but no end seals.Measure the distance between the top of the block and the bottom of the intake on the ends.Subtract about .060" and thats how much you need to take off the distributor boss.Good luck

More info here:
http://www.hotrodders.com/forum/427-tall-deck-information-book-129294.html


Also found this:

88961161
intake manifold, zz572/620 engine
• Aluminum single plane intake manifold is used on the
ZZ572/620 engine
• The carburetor flange is for a 4150-style carburetor
• Use intake gasket P/N 88962213
• For tall-deck blocks