Multiple SPI devices with different logic levels
The 74LVC245A has tri state outputs; taking the \$\overline {OE}\$ pin low enables communication from A to B or B to A (depending on the level on the DIR pin).

The outputs can have a state of High, Low and High impedance (Z).

You can therefore not tie the outputs together as these are push-pull outputs when enabled.

You could follow the '245A with a multiplexer to use a single pin at the micro.