the automotive world quit using the SBC in 1999 (2000 on some models) when the GM cars and trucks switched from the Gen 1 SBC to the LS motors.
your 2004 block and heads are the same as the automotive 1996-2000
the marine world buys their motors from the GM industrial division.
so you have to get a motor from GM, or one of the crate sellers like michigan motorz.
since your block is busted from improper winterization. its a good chance your exhaust is busted too.
www.michiganmotorz.com
you have your choice of new or reman
However you can also buy a GM block from GM,
https://www.gmperformancemotor.com/category/SB134.html
stuff it with a SCAT stroker rotating assembly
and build a 377 (6.2) for about $4400