i'm assuming he wants to build both, only has room, dollars & time for one at the moment, that's why he asked which one YOU would keep, i'm sure he'll build THAT car the way he wants.
i must have missed that the 71 was original 455, that might lean me towards the 71 IF you could find matching parts again.
based on the info you gave though i'd still keep the 70.
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71 Formula 400, Castillian Bronze, Saddle Interior:
https://youtu.be/cfEv-1vKc0k