I considered the ZZ-4 replacement engine, but I really wanted to get away from the carbureted engine and also find something that had a roller cam and fuel injection.  My first thought was at trying to install a 2004 Yukon, Gen IV 6.0L we had on hand.  When trying it as a fit we found that too much modification on the frame, steering and A-arm clearance was not really feasible. 

I started looking at the L-31 Vortec engine which was in the 1996 Tahoe’s and Yukon’s VIN code “R”.  We managed to locate one with low mileage 40K complete with computer and wiring harness.

I considered using the serpentine belt system on the L-31, but it would have required complete relocation of Alternator, AC compressor and some clearance problems with the power steering.  The L-31 block external bracket mounting bosses are identical to the L-48, so I remove all the serpentine and replaced the serpentine water pump with a short stock corvette water pump.

The new engine is running at about 300HP plus which is about double the old L48.  In town mileage is around 15 mpg and highway should be over 21 mpg.  With the 700r4 and 3.08 rear-end 2000 rpm is right at 76 miles per hour.  The 700r4 is setup with a switchable electric locking torque converter in 2^nd, 3^rd and overdrive. It really is nice to have a friend like Dana with a shop and lifts to help bounce the ideas off of and work with. Dana owns Alert Services in Las Cruces, NM and is an avid car buff and friend. 

If you are interested send me your e-mail and I will send you a copy of the step-by-step with pics in MSword or .pdf . 

Lee (technut@comcast.net)