A 4.3 is a V6 engine. It's not as easy as a "drop in and go". You'll need a high pressure fuel pump and a return line from the engine back to the fuel tank. You'll also need to have "bungs" welded on your exhaust pipes for sensors. You need to have the ecm re-flashed if you buy an after market stand alone harness. Now where to put your water and oil senders for your aftermarket gauges? The existing oil and water sender provides critical info to the ecm so they can't be replaced. It's best to invest in a Haynes Repair Manual to refer to all the efi conponets and wiring.
I'm going thru the very same conversion but with a V8 5.3L Vortec engine and I can tell you it's not a "plug and play" effort...but in the end it'll be worth it
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