1968 corvette convertible with 1969 427 engine

1968 Corvette with a production date of 07/19/1968. I was told engine wasreplacedunder warranty. The 427 engine has a date stamp of F 17 9 Block casting # 3963512 It has 4 bolt main bearings and the large threaded plug in the block over the oil filter for oil cooler. It has 12.5:1 free floating pistons,large connecting rod bolts,7/16pushrodsand solid lifters. These items are all original GM factory parts Making me believe that this is an L88 High Performance replacement engine. The oil pan is an original GM trap door 6 quart oil pan. The transmission is a muncie 4 speed # 3925660 and rear end is a posi trac 336:1. Cyl. heads had hair line cracks so I replace them with new and now car burn unleaded fuel.