3.4 DOHC

Ok I hope you realize that NOTHING from your 2.8 can be used on a 3.4 TDC motor.  I think you can use the exhaust manifolds from the 3.4 TDC and modify it to work with the Fiero exhaust system. 

The 3.4 TDC motor is probably my favorite engine transplant, if it was not such a huge PITA to do I would do one myself.  That 7000rpm redline and simply exotic sound is what turns me on with that setup.  As for cradle you can use your cradle just fine, however it should be removed and re-enforced as the 88 cradle is a really weak cradle. (much weaker than the 84-87 variant) 

The Isuzu 5spd in your 88 (assuming you have a 5spd) won't last very long, maybe a year or 2 before it grenades.   The Isuzu on my 4.9 lasted 6 months to a year before I had to change it. Been through 4 of them.  

There will be major wiring to do, some metal fab work and welding.  Note the 3.4 TDC wiring is MUCH more complex than any other V6 conversion.  Only ones harder are the 4.6 V8 Northstars and the new 3.6 GM DOHC motors.

        I say if you have time, money and a shop to do it in, DO IT.  You'll love the car.  However if you don't know how to work on cars, don't have access to a welder and know GM EFI wiring you would be better off doing the 3.4 Pushrod motor from the early 90's Camaro.  Its pretty much a bolt in for your car, and if you find a complete Fiero V6 wiring harness its all plug and play.  The engine has the same mounts as the 2.8 and can use all the 2.8 fuel injection.  So you swap on V6 Fiero wiring and sensors, plug it into a Fiero V6 ECM and drive away.   Its not nearly as fast as a 3.4 TDC, but its a HUGE upgrade from a duke.    

Sorry I have been up for nearly 24hrs and glazed over the part about the 4cyl.

Ok the V6 and 4cyl cradles are the same.  There is no difference in them.

The Isuzu 5spd is what was used on all 4cyl Fieros' from 85-88.  The Getrag 5spdswere on V6 Fiero's from late 86-88.   If both your shift cables come over the trans and have one mounting bracket for the 2 cables its an Isuzu.  If one comes from under the trans and goes up, while the other goes over the trans and comes down, then it is a Getrag.  I think I have a pic of my Getrag in my 88 and my Isuzu in my 85.  If I can find them quickly I'll post them up.  If not I'll go and snap a few shots in the Morning and post them up for you.  One sorta way to tell, all the Getrags had a Dipstick for the Trans, where 75% of the Isuzu's did not.  You had to pull the VSS to check the fluid level.

Isuzu Cables, not they run side by side and go over everything and then down to the trans.

Ah Frack, I had a big reply written, hit the wrong button and lost it all.

Ok Short reply.

Link is fixed, I screwed up the markup tag.

Should load fine now.

          You know who I am? But for the life of me I can't remember who you are? I don't recognize the nic.

        Drop me a PM to jog my brain. I think it needs a jump start at the moment, and maybe a shot of nitrous down the throat to get it fired up.     Well I'll talk to ya all in the morning.

In a nutshell - everything has to be fabricated.

The engine/tranny combo has to sit very low on the cradle, or the massive heads/valve covers wont clear. I did the harness and assisted on the install in another guys car about a year ago.  It's tight.

The OBD1 versions (up to 93) are not as good an engine, but - the install of them is WAY (!) easier.