So how viable is a swap from a 4 speed Muncie to a 5 speed Isuzu in an 86 V6? Different shifter, different shift cables?, cable bracket for tranny?

I did that swap to my very first fiero. The 4 speed shifter can be reused if you take the reverse lockout off and the clutch and axles are interchangable.

Cables, Mounts, Slave and Throw out bearing are tranny specific, so you will need to swap those parts.

The 4 speeds have the reverse light switch on the shifter and the Isuzu is on the tranny, so you will need to run 2 wires to the tranny to make it functional (or do nothing and just not have backup lights).

quote Originally posted by fieroguru: Cables, Mounts, Slave and Throw out bearing are tranny specific, so you will need to swap those parts.

I've done this swap twice. Most recently, last week. The 85-86 V6 4-speed slave can be used with the Isuzu tranny, so save yourself some bucks and reuse the slave you have. Having changed the GT from a 4:10 4-speed to an Isuzu, my around town MPG jumped from 21 to 28 MPG. I'd expect over 30 on the highway. If I could only remember that I now have a 5th gear.