To get the application code correct you first have to determine the year of casting. The easiest way is to get the julian date code by the distributor hole. If not you can get way off track with the block code as they were repeated through the years. If you have a block code of "WT' for example you either have a '66 389 or a '71 400. Of course it gets a little trickier when blocks were cast in the fall or summer before the model run, but it gets you in the ball park.
I think in this case with the WT code it is apparent about the block I.D. I was informed recently that 68 & 69 carried their own block casting # so probably 70-72 would be the same block casting, all with the same WT code. This can confuse a person quickly without all the #'s together.
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John
1972 Pontiac Lemans (daughter's car) 2005 Pontiac Grand Am 2004 Ford Explorer Sport Trac