The 1996-2000 L29 7.4L big blocks are great engines. Much more dependable and durable than the 6.5L diesel of that era. L29’s had multiport sequential fuel injection, all of the latest sealing technology to prevent oil leaks and the “Vortec” style heads flowed very well. The advertised 290 HP rating at that time was very conservative. You can pull a lot more power out of one of these engines by just simply having a tuner add a hot tune calibration into the ECM and bumping up the fuel pressure 2 to 5 psi. The only other big block that surpasses an L29 in performance is a L18 8.1L which is similar architecture but a completely different animal.
The L29 doesn’t have any major durability issues other than the distributors can build up condensation and cause premature failures of the moving pieces. Easy fix is to install a $200 GM Performance Parts RamJet 502 distributor with upgraded internal components.
L29’s are known for cracking exhaust manifolds and their normal chemical dependency on oil. GM’s oil consumption spec was 1 qt per 100 gallons of fuel used was considered normal for any big block gas engine that era. While most went well beyond a 1,000 miles between adding a quart of oil many will need a quart every 1,200 to 1,500 miles. The stock 8.1L in my 2001 Silverado that I purchased new has used a quart of oil every 1,200 miles like clockwork since day I brought it home but the 8.1L in my 78 K10 doesn’t use a drop between the 3,000 oil changes which still surprises me.
Fellowtraveler’s comment on the passenger’s foot getting into the ECM wiring isn’t accurate on a 1996 or later GM anything, as the ECM began being mounted under the hood in 1996. I suppose the foot deal could apply to older TBI trucks with ECM's under the dash if someone hacked up the area installing a stereo or something and left harnesses exposed. I’ve never seen the under dash ECM or harness causing an issue on anything GM.
Ahh, the good ole trusty L29...