GM switched from L35 to LU3 in MY2003 for the S10 Blazer. S10 Blazer production ceased in 2005 but they continued the LU3 for the Silverado 1500 base through 2013. The 2003-2006 LU3 in a direct replacement for either another LU3 or the L35, but in 2007, changes were made to the LU3 including

• Electronic throttle control
• DIS ignition, removing the distributor and drive gear
• A 58x reluctor, redesigned timing cover, and remilled block to accomodate said timing cover

The 0411 (Gen III?) ECM/PCM has no provision for IAC and no way to read the output of the CKP from the 58x reluctor.
So the options are:

1. Replace electronic throttle body with cable throttle body
2. Install distributor
3. Switch reluctor

Throttle body is easy enough. I hear the cam still has a gear to drive the oil pump and the shaft for the distributor is still there. Is it plated off? I hear of this "dummy shaft" used to drive the oil pump. Is that accessible from the alleged distributor shaft? Or do you have to take the pan off and get it from the oil pump side of the shaft?

Now, the reluctor. It would be great if you could just swap the 58x reluctor for a 3x reluctor (I have all parts from an '02) but the reluctor and timing cover on the 07+ LU3 is much larger, necessitating either swapping the timing cover or having a larger 3x reluctor. Swapping the timing cover is NOT possible, because the block is milled for the larger cover.





However, a larger reluctor is possible. EFIconnection.com sells one for this purpose.



EFI Connection, LLC - Item Details

It is ridiculously expensive, but maybe I can have a machinist turn and mill one cheaper. It looks like everything is 60* apart, with one "tooth on the midpoint line of the woodruff key.

Am I missing anything?

The reason I'm doing this is there are many 2013 4.3L LU3's on Ebay with low miles and sometimes cheaper and more plentiful than an 03-07 LU3. Thanks in advance!

 

I realize this is from 2015 but I wanted to add some information to it in case anyone else comes across it like I did while searching.

I bought an LU3 crate engine and swapped it into my truck. The timing cover is no issue. Still the same 6-bolt pattern as the L35. My new L35 cover bolted up perfectly and hasn't leaked a drop in 6 years/12k miles.

The engine as a whole was plug n play. Bolted on the flexplate and timing cover, then finished it off with my cleaned up oil pan. Dropped it in with new motor mounts from Anchor and it went right in. Buttoned it up and finished exhaust and haven't had it apart since except to replace the lower intake the day after I finished the swap.

Anyway. That's all I wanted to add. The L35 cover will bolt right up. Motor mounts, too. So will everything else. Since my truck is a 2001, even the EGR system went it without a problem.