You can search the archives to get a more complete picture but I'll make a stab at it since I just finished the process of going from a 302 to 408W.
* Of course, new engine, carb, and accessories.
* Upgraded radiator to keep the beast cool.
* Upgraded transmission and clutch (G-Gorce gear set in T5) to handle the extra torque.
* Upgraded fuel pump, added regulator with bypass. Make sure the fuel lines can handle the task (3/8" hard tube ships with carb kit, some have gone to 1/2").
* Exchanged 4 into 4 headers for different engine dimensions.
* Added an oil cooler to keep temps down at the track - but it's not essential.
I highly recommend it, but it's not for the faint of heart. Also, starting out with this much HP in one of these cars could be a recipe for disaster. Take it slow until you get used to it. The tires will not last as long and they WILL take a beating. I need to go wider in the rear. Anyone have a good set of tires and wheels for cheap?
I almost forgot one of the major points of your question - EFI to carb. You get to dump/recycle the computer. The wiring will change a little. There are many threads discussing this effort. I am not experienced in this part of the task.
All engine management stuff will be removed from the 302.
Oil pan, pickup and associated hardware
Intake manifold (your going from EFI to Carb so a new one will be required)
Depending on the year block the cam/lifters are different (you will have to change springs on your heads to match which cam)
351 uses 1/2" head bolts where the 302 is 7/16")
After all of these points are taken care of pickup at the same point as you would converting a 302 EFI to a 302 Carb.
Breeze has the carb fuel pickup #70099 You'll need atleast 3/8 fuel line.
Also use a Carter electric fuel pump #4070 Low pressure, high volume. No need for a return with this pump.
Harness, If you have the mustang dash, you just need the two connectors from an old computer harness. Makes it a little easier. They are round, black and a grey one, nxt to the computer. These will go to your sender units, oil, temp etc.
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