[MySons68C20]

"Although most 5.3L LS blocks are cast iron, GM manufactures aluminum versions for the LS4, LM4, and L33. Like iron 5.3L blocks, the aluminum units share the same 3.780-inch bore. Unlike its iron counterparts that can be bored to 3.900 inches, the iron liners in aluminum 5.3L blocks can only be opened up .010"

.030 over is common on the iron blocks and you should not have any reliability or overheating issues.