What do I need for an L67/F23 swap?

I've done it, I think I have the build thread on here too, I'll check later.

Stock Fiero axles from a manual trans will work fine.

You will need to make mounts for the transmission, f23 has completely
different mount points.

I think there's a way to make stock shift cables work, one will work
anyway, one should be longer, forget which one. You'll also need a
custom shifter bracket on the trans.

Adapter for the clutch lines. You can make one, or there are a couple
online you can buy.

From what I can see, HTOB spacer depends on clutch model. Looks
like if you don't need to clearance the diff bump in the bellhousing, you
will need a spacer. I've only ever seen people use 1/4" ones. Spec sells
them.

I did not need a spacer with my clutchnet clutch, but dd have to grind
away some of the bellhousing to make it fit.

I believe all axles are the same for manual fieros.

I got the stage 2 I think, the one they have listed for an 88 5 speed v6,
rates for 310 torque. I'm quite happy with it, it's quite smooth and has
no problems holding the power.