Where does the underhood fuse block get it's power from? I'm trying to wire up my '88 Trans Am with a '94 LT1/T56 and the motor came with the underhood fuse block harness also.
The PCM gets the power for the injectors from the 2 7.5 Amp fuses in the underhood fuse block, and power from the Ignition fuse (10 amp) too. I have the 4th gen C100 connected to the engine harness I just don't know where the power will come from.
There's a lot of fat red wires that go to the relays in the underhood fuse block....do these fuses (9,10,and 11) get power from those red wires too?

 

Your best bet might be getting a holy book haynes for the wiring schematics on that engine. Also gives you info on the new motor. (but you knew that already)

Alternative could be going to a dealer & ask to see a wiring schematic for the 94 car. IT helped me tremendously w/my swap and it was free

 

Im not sure since I never even used that extra wiring harness. Might want to check www.shbox.com.

 

all the 4th gens I've seen have had fuse/relay boxes on each side of the engine bay.

 

Well I've got my thirdgen manual that goes from 82-94. And I've got the '94 Chiltons. I work at a dealership and can have access to those, I just need to know how ya'll hooked up power for your injectors?
I cut most of the wires to where all I have going to the underhood fuse block is the fat red wires that go to the junction block and the 4th gen C100 wires.

 

I just spliced into the pink wire onto the injectors and gave it power from another wire that got power after the key was turned.