I insisted on nothing!

From the advice here, going from 3.3V to 5V was not an issue as the 8051 would see 3.3V as "1" anyway.

My concern was that the 8 bit wide 245 chip I'd found was a real overkill, and required directional driving.

What I found later, having been given the steer, was a 2 bit 2 Vcc buffer chip. I have now arranged for 2 of these, each using a single channel in one direction, with a fixed direction bias.

I am confident this will work. It is still possibly over engineered, but it will cost me less to do it this way then to try to debug the potential issues of not doing so.