in reply to Trouble getting a local DBD::Oracle to work (Dynaloader!)

DBD::Oracle object version 1.74 does not match bootstrap parameter 1.64 at .../ line 223

That's usually a sign of a botched install.
The version of your is 1.64, and it wants to wants to bootstrap object version 1.64 (where "object version" is the version of the Oracle shared object that perl builds and installs as part of the DBD::Oracle build and installation process).
However, the object that it finds is still version 1.74.

So ... it seems you've successfully downgraded from 1.74 back to 1.64, but the compiled/XS element of DBD::Oracle that's being found is version 1.74.
Either you failed to properly build and install DBD-Oracle-1.64, or the "object" for 1.64 has, instead of overwriting the "object" for 1.74, been installed into a different location - one that occurs later in @INC.

Are you sure you built and installed DBD::Oracle correctly ? (Replacing version 1.74 of with version 1.64 of is not sufficient.)