Buddy found a 5.3l and a 4l60e with a standalone harness from an 03 tahoe. Guys says he has more like it, how much work would that be? If I sell some stuff I might be able to swing it after the first of the year. Gotta get that tranny fixed...
Would this engine be worth the effort?

not as powerful as the 5.7 liter LS1, or the 6.0 leter LS2, but made from the same stuff. Swap would be the same, you'd need a fourthgen oil pan and thousands of dollars worth of bits and peices from ATS.

The 5.3's are good engines. I know the heads are very similar to the LS1 / LS2 heads, intake ports are just as good, compression is lower than the LS2's 11:1. I'm not real familar with the cam they use on those stock, you might want to step it up a bit, it is a "standard" truck motor after all.

Just asking questions Jim. I dont have the money to do it. But research never killed anyone. I would like to do it in the future tho...guy wants 1900...wow.
Got to concentrate on a dependable vehicle for the wife.
this kinda stuff keeps my mind busy tho...thanks for response.

I've seen several people over in the Conversions & Hybrids forum on ls1tech with 5.3's in first gens. '03 Tahoe would be an LM7 or L59 (flexfuel). 325cid, 285hp @5200 , 325 ft-lbs @4000, and those numbers are SAE Net through cats and an fairly restrictive muffler. It's a nice little motor for a driver, and heads/cam/intake/headers/accessory brackets/oilpan/flywheel/mounts/etc all interchange with the LS1 from the F-body and 'Vette.

Pretty much everything that applies to the LS1 swaps applies to the LM7 as well, with a couple of notes:

You might have hood clearance problems with the truck accessory brackets and truck intake. F-body parts bolt right on, but it's extra cost. The balancer (integrated pulley) also needs to match the accessory brackets. The truck pan hangs down way too low, so you'll need an aftermarket swap pan, or take your chances modifying an F-body pan.

I believe an '03 Tahoe is ETC (Electronic Throttle Control, aka drive-by-wire), so you either need an electronic gas pedal and module from a late model GM car, or you can put an older cable-style throttle body on it, move a few pins around in the PCM wiring harness, and reflash the PCM with software for an Express Van.

I've got a ton of pics of my LS1 swap at http://www.blown.net/ls1swap/. The biggest problem I ran into was all the other crap that I decided I need to replace/upgrade at the same time as the engine swap (rear end and brakes, rear suspension, gas tank, hydroboost, steering box, interior, ... ).

Hell ya, with notes like above. That was plan A for my 67 because you can find low mile complete setups cheap, as in under $2000 if you look. Exhaust & tune away from 350hp. 2wd trucks, lots of them out there.