Be me. 2010. Friend of a friend was selling a white 95 Firebird Formula that he wasn’t gonna get around to do anything with. Bad tranny, blown engine. Copped it for $800 plus I threw in another $100 for the engine stand the motor was on. Got enough time and money together. I rebuilt the tranny with some performance upgrades, shift kit, clutches, servos, accumulators, springs, 3000 stall converter. Sent the block and heads out the machinist. Bored .030” over and decked, hypereutectic pistons, forged rods, moderately aggressive cam, 12.8:1 CR. I put well over $8k in the rebuild. The car came with a Borla catback. It sounded wild and acted just as good. Daily driver. Didn’t even put 5k mi on it. Long story short: I was in a hurry coming off a right turn ramp at a light, was leaning into the pedal, it shifted into 2nd coming out the curve and broke loose. Started fishtailing, over corrected several times and ended up swiping the nosecone across a jersey wall in the median. It sits in the yard for 4 years.

I finally found a suitable replacement on Craigslist last Thanksgiving. 97 Formula, red. $700. 8/10 body, bad head gasket, shot crank bearings, but it fired up and drove. It was sitting in a wooded area for 6-7 years covered in leaves, floorboards all had puddles and it was really mildewy inside. No matter. I finally had a nice looking car to drop my drivetrain into. And possibly interior.

So I get a little bit of money and time recently and decide to do the engine swap. Drop everything out the bottom. (And let me tell you… WAY easier than fighting it out the top! Disconnect a few things counterclockwise from ECM to the fuel lines, a handful of miscellaneous connectors, driveshaft, and 4 bolts on the tranny and 6 on k frame. And a few on the shock towers and its out in under 4 hours.) Engine 1 out. Unbolt engine, put k frame back in with 2 bolts and one bolt on each shock tower to roll out. Lather, rinse, repeat. Engine 2 on the floor.

Looking at the two side by side This is when the realization sets in: I have overlooked several major details in going from an OBD1 to OBD2. (Yeah, I could have just put it in as is. I don’t know what I was thinking.) I had remembered I’ve read many times it’s real simple to switch between OBD2 and OBD1 for tuning purposes: just a computer and a knock sensor swap. I don't know why I thought it would be just as simple the other way. OBD1->OBD2 is much more difficult. It’s been one nightmare after another.
Problems I’ve encountered:

Different exhaust, one cat for each side and post-cat O2 sensors.
Different tranny tail shaft (VSS and connector).
Different harness.
Different coil
Different knock sensor.
Wrong crank key, no reluctor ring, wrong timing cover and crank hub, no CPS.
Different air pump connector.
And some misc pieces on top connected by vacuum hoses.

Basically, I’ve stripped down the front of both engines, which pretty much stalled my progress. Anyone who has ever owned an LT1 knows it’s a huge PITA. I also had to do some undercarriage rust treatment on a few spots while the engine is out. K frame and rear are really rusty, so I decided to swap both out with my other car. The parts list just keep piling up:
Polyurethane motor mounts, tranny mount
Radiator
Exhaust gasket, manifold gasket
Exhaust studs
Spark plugs, Wires
A/C Compressor
timing gaskets, water pump gaskets
oversized oil filter
$200 in fluids (Mobil 1, synthetic ATF, coolant, gear oil, steering, brake)
I'm sure it'll need brakes and rotors all around.

I’ve just been pulling my hair out. I had to share with someone.
I'll post some pics this weekend.

 

Since you have the whole donor car just swap everything over.. You should be able to use your old transmission but you have to get a special tune for the pcm to lock up the converter correctly..

 

Well, yeah. Essentially, the only thing that's gonna be left intact on the the red car is the body and frame.

 

if putting in a obd1 motor into a obd2 car, just harvest the timing cover from the original OBD2 motor along with the crank position sensor wheel and the knock sensors from the obd2 motor. Also use the OBD2 motor damper hub

 

What he said^^ just swap everything over..

 

Yeah, and the crank key to accommodate the reluctor ring and shorter hub. I tried to go the cheap and lazy route and ordered a timing cover from Autozone, but when it came, it was plastic and only had holes for the crank and speed sensor. NONE for optispark or water pump. I sent it back like "who can even use this? the stock engine doesn't come with an electric water pump and coils on every cylinder" and they looked at me like I was the crazy one.

Does anyone know about why the tranny tail shaft is different for 96-97 only? It has the VSS sensor on the opposite side and the connector is different. Can this just be unbolted and swapped too?

 

Sounds like they sent you a Vortec timing cover.. And I don't see why the 96-97 tail shaft wouldn't work..