['63GENIII]

Ive got both at the moment. 2004 Yukon XL with a 6.0 and '63 K10 with the L29 and 5spd. So, kind of an apples and bigger apples comparison for me. The 6.0 had been virtually maintenance free with the exception of external regular wear items (water pump etc.). No internal hard parts but it does weep oil from the timing cover and valley area. 125k on the clock.

The L29 (Vortec 7.4) is relatively new to me (200 miles) and replacing a carbed 396.

While we've used both vehicles for towing, I have always preferred the BB over the LS. Just seems like the LS is always straining a little more than my comfort level can accept. And while the 396 just seemed to lope along no matter what it was pulling, I can tell that the L29 has WAY more torque (and rotating mass) than the 396 could ever hope to produce or for that matter the 6.0.

The L29 does have a cam, injectors and a tune so this may be an unfair comparison. I would really like to see what the 7.4 would be like with a 4L80 in a 2wd truck with a decent suspension.

I really dig this last generation of Big Block and the cool parts that it came with. It does have a roller cam block, fast burn heads, one piece rear main seal and pan gasket, o ring type front timing cover, sequential port injection just to name a few things.

They do make manifolds for the L29 if one really wanted to run a carb but FWIW theres really no point after experiencing an injected Big Block.

Im not sure how many miles were on the engine when I got it but my machinist guessed it was over 150k. It had such low wear on the rotating assembly that I was able to reuse the pistons (please don't flame me, I was near broke at the time and still am LOL), hone the cylinders and polish the crank. All standard bearings and rings. He believed that the lack of wear was from regular maintenance AND the fact that the fuel injection meters fuel so much more efficiently resulting in less carbon in the oil. The heads did get a thorough valve job and that was it.

As far as mileage, the 454 is too new for me to get any numbers. The 6.0 and the 396 were about dead even though. Im fairly certain that the 454 will get lower #s than the 6.0 and 396... especially if I can't learn to keep my foot out of it!