Since this is being manufactured to an AMS spec then you could also look in the MMPDS and see if the two tempers are listed in the same line. If they are listed with different design properties (even if the spec properties match) then they cannot be interchanged.
If it look for plate I see that T73 is listed as having different properties than T7351.
However under extrusions T73, T73510, and T73511 are all listed as having the same properties.
Then following are the different tensile and fatigue curves for each temper.
Changing temper in Al can be very risky.
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P.E. Metallurgy, Plymouth Tube