Chevy was not supposed to be involved in racing but there was a lot of "research" being done on 500+ hp motors - both iron and aluminum. L88 rods were not designed for the trailer towing package.
Jim M. did say he remembers the 68 Yenkos were 427s with MV code but other opinions exist. I believe the 68 Yenko was done using the COPO system 9737 because of the 140 speedometer and other hi po parts. I don't know if the 68 Yenkos were built with a special MV L78 or a MV L72 or something else. What I am saying is if 50 were built with a 427 or if 50 were built with a special 396, I would think that Chevy would have asked NHRA to make it legal for racing. I am sure the racers in Chevy engineering would have loved to build 50 L88 1968 Camaros since the 68 Hemi Dart/Baracuda and 68 428CJ Mustang were on the drag strips. Here is a quote from Jim's post "Cole and Estes also wanted to be able to track these vehicles for ownership, as well as warrantee expense. They had the Chevrolet Product Planning Department issue a special engine code for the "427" engine that went into the 1968 Yenko Camaro COPO 9737. That code was "MV". Tonawanda records show that a total of 79 engines were built in 1968 with the "MV" engine code. I don't know if all of these engines went into vehicles (some were held for warrantee), but I do know that they were (L72) 427's."
https://www.yenko.net/ubb/Forum1/HTML/000379_2.html