It really depends on who you talk to on what the use of them was. Some of people will say it would have been the LTX block thanks to the LS1 it never was made in huge numbers. Been told there are less then a dozen of them. Looks to based off the bowtie block. It also have knock sensors on both sides like a B-body and was used for spark sweeps. When this engine ran it had LT4X heads on it and the first gen hot cam. Weighting the block it comes in at a stought 178lbs.

Yes it has been sitting around my garage for a while.

Also one more thing on splayed caps they are cast as a 2 bolt then machined