2wd-K5

unless it is a sluged up toyota ;P
seriously though, the main difference is the heads, they are more efficient and it doesnt have siamesed exhaust ports like the old ones did. old small blocks overheated when pushed hard because of this and wore out valve guide seals whick in turn made the engine burn oil (old small blocks were famous for this) im pretty sure the newer small blocks have aluminum heads and iron blocks. a freind of mine has over 450k km on her 99 (2nd year of the engine and they have improved since then) it has a 4.8 and the truck is falling apart around the drivetrain (constantly repairing odd things) it is funny because she has a new engine trans and rear and front diff for it, but everyting else is going wrong lol
hope this helps

silverado13

i have a 97 Z71 and ive been through 4 transmissions so far but im one the original motor with 239,000 on it, even though my engine runs fine with good power still im going to be doing an LS1 swap pretty soon

Aw7233

I have 176,000 miles on my 01' 5.3. It runs strong. Slight lifter tap in the morning but goes away when warm. Only thing replaced on it was water pump pully and a new belt while it was off.

5.3Forever

I have a 5.3 in my 1999 2wd with almost 240,000 miles on it and it still runs awesome, the only problem is the intake manifold gasket going to ****. im not sure if they fixed that with the newer trucks but ive heard its a common problem. other than that its the best engine ever made. has power, speed, decent gas milage, lasts forever if you take care of it.

JK23112

I now have 102,000 miles on my 2004 Silverado now and she's running strong. I intend to keep it, as I sure cannot afford a new one. I also will keep my '02 Sentra for another two years and pass it onto my son when he begins driving (Gasp!). It has about 130,000 miles now, but I got it repainted & had new struts installed recently. It serves as a great commuter car because it uses half as much fuel as the truck.

My friend with the '02 Silverado now has 180,000 miles on it -- and his is also equipped with the 5.3L V8. His runs strong and he's had no trouble with it at all. I hope I can get that out of mine - and then some!

Exhausted

The old 350 -5.7 is a gen II small block
The the 5.3 325ci is a gen III small block and the architecture is entirely different
Four head bolts per cylinder, 6 bolt mains......
The 5.3 is based on the same 5.7 LS1/6
The 5.3 had iron heads in 99 but they are aluminum since 00'
The real beauty is in the valve train and heads
LS style heads out flow genII heads by a lot!
The is a ton more differences but those are them main ones
The gen IV the new style 4.8-7.0 and based on gen III but improved

cornfed1589

282k on my 5.7 vortec. Took the fan off water pump. Put electric fans. Cold air intake. Flowmaster muffler. Sits on 35's with 4.56's in my rear end.Still has tons of power,and does not burn a drop of oil. Just an awesome motor!

chuparroso

My 02 Tahoe is approaching 230k and still runs great. I recently got it from my sister, and she purchased it from a county auction. My sister went on a lot of road trips and I have to as about a quart of oil after 2.5k miles and change oil and filter after 4k.

I'm planning on doing major work once I move out of my apartment and into a house with a garage: cylinders bored, engine block resurfaced, heads resurfaced, maybe cams and lifters after I do research. The only other problems this trick has had is intake manifold leak and gas pressure sensor malfunction. Great dependable. My 'hoe is like a rock.

Fishinfooleric10@aol.com

197000 before the motor blew but my fault that it blew on 99 z71 5.3. I still kept driving with a blown head gasket so I can't be mad at chevy because it was all my fault. All i know is the that motor and the junkyard motor i put in there both kick ***. I can burn them tires down the street no problem. Friend 04 4.8 160000. Other friend same truck as me 260000

JK23112

108,xxx miles on my 2004 5.3L Silverado 1500 -- and still going strong. Knock on wood! (I bought it used three years ago with 74,xxx on it.)

My friend has a 2002 and is pushing 190,000 miles on his 5.3L -- no problems so far. I actually bought my Silverado because of his good luck, as I am a Ford guy (or used to be) when it comes to trucks.

The main thing is to keep the oil & filter changed frequently. The old "small block Chevy" has been around for nearly sixty years for darn good reason.