So I picked up another LS1 block... turned out to be a LS6 with the LS6 pistons less the cam. I am shopping for the cam now. I will be having the heads reworked also.
LS6 block
LS1 Block
positives:
The LS6 shares its basic block architecture with the GM LS1 engine, but other changes were made to the design such as windows cast into the block between cylinders, improved main web strength and bay to bay breathing, an intake manifold and MAF-sensor with higher flow, a camshaft with higher lift and more duration, a higher compression ratio, sodium filled valves, and a revised oiling system better suited to high lateral acceleration.
The LS1 pistons are made of a metal listed as "M124" - the LS6 pistons being "M142" which has a higher nickel and copper content. The LS6/m142 pistons are stronger and expand less under high temperatures, thus allowing them to reduce the bore clearance. Reducing oil consumption and increasing overall and high rpm durability.
further information borrowed from Ruthless pursuit of power.
Obviously, cutting windows at the bottom of each cylinder
reduces the strength of the block’s key structural area, the
main bearing bulkheads. With 40 more horsepower, 400-500
more rpm and even more powerful derivations of this engine to
come, the block needed to be even stronger than it would be
without the windows. It doesn’t take a rocket scientist to figure,
in their ruthless pursuit of power, Dr. John and his engineers
had to do more than simply reprogram their CNCs to cut those
windows.
Finite element design work along with a lot of thrashing
engines to death (in a few cases, literally) on the dyno
eventually resulted in the special LS6 block having both the
bay-to-bay breathing windows and more overall strength than
the LS1 block