Lyn, changing from carb to EFI will mean that the cars entire fuel system will need replacing. You'll need to buy a different fuel pump, fuel lines, fabricate a return line, etc. Lots of $$$ to change an almost complete car.
To change from a 351 to a 5.0L motor will require new exhaust headers, as the existing ones won't fit the smaller motor. More $$$$
Wiring changes to wire a 5.0L over and above what you already have in place will also cost more $$$$$$$$
Buying a replacement 351W will most likely be thousands of dollars cheaper than converting back to the EFI 5.0L, and you'll have more power with the bigger engine anyway
