what is required of a switch to the 5.3?

[Aaronoregon]

Just got done with one into a '46. They are actually one of the best, easy mods you can do for the money. Very readily available in junk yards now days. My daily driver is a 2001 Silverado with a 5.3 and I just turned 232,000 miles with no issues so far. Doesn't burn any oil and has great oil pressure. Like said above, you want to buy it complete! Everything! Motor, accessories, harness, ecm, etc. I have been getting them with the 4L60E attached complete for $1500-1800. You will have to redo the fuel system. I have been throwing a Walbro tank in the tank and running a corvette regulator and a Racetronix harness. Just to upgrade the fuel system to run the injection will cost about $300 or so. You will also need to get the ecm reprogrammed to delete Vats and rear o2 sensors. Not a big deal at all. These engines will get you great reliability and average about 20-22 on the highway. Good luck!