Going by the date code the block was cast on Sept 20th and the heads on Sept 30th of 1982....Since the intake has the E3 casting number in it I would assume this is a very early production 1983 motor or someone has swapped the intake...

As far as deciding which engine to build the engine on the stand would have the 50oz balance and the one in your truck would be 28oz so the flywheels and balancers would not interchange between the two..This may not have any influence on which one you build but I thought I would mention it...

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1968 mustang..408 windsor.Vic jr heads and intake.Pro Systems 950HP holley, 1 3/4 hooker super comps,Custom CI solid roller camshaft,Probe shaft rockers, 4 speed with 4:11 detroit locker.