My old Chevrolet Power book (5th edition) lists and L-88 part number 3970699 as:
"Engine Asm., Partial 427, L-88, Open Chamber Design"
"Engine asm. partial" was Chevy talk for a short block.
Here is another thread where someone had the same short block for sale.
https://www.yenko.net/forum/showthread.php?p=737591
If the naysayers need proof, I can scan that page in the book and post it here.... maybe.
Not too tech savvy lately.