I want to swap a 6.0 in place of my 5.3. I have a few questions. 1).Will the stock 5.3 computer and fuel system be useable and 2). If so, can I still use my HPPIII to tune the ECM with. I would think that if I am using the 2000 5.3 computer, then I should be able to continue to use the HPPIII??? Also, where might one find a 345hp LQ9 complete engine? Any help will be appreciated.

 

you can use the 5.3 computer but the 6.0 would benifit greatly from a custom tune, when i did my swap the only programing i did at first was to up the idle a little. the fuel system is the same. you can use the hpp3 but a custom tune would be better, i think you can buy a new lq9 for around 3k, someone around here said that anyways.

 

parish8 is correct on the tuning. I was disappointed with the swap until I went with LS1edit. You have got to tell the PCM it is a 6.0, turn COT off, get air/fuel ratio to approx. 12.75-13 to 1 and get the timing up to around 25-26 degrees at WOT before you can really feel the extra cubes. I paid $3200 for my long block from the local dealer.