Looking back at your pictures it does not look like you have the same thermostat housing that the LS1 has, but this may work. I got this tip from one of the LS1-LS6 build books, I can find it when I get home tonight. Original Gen III motors had the thermostat build into the housing and had a wax motor that open and closed it. You can easiliy take it a part and place a spacer in the mechanism that will cause it to open sooner. It does not hold it open. On the one I messed with, I used an 1/8" ferrell from a compression fitting and sanded it down to the recommended thickness (it's in the book I will find tonight) and this was supposed to have the thermostat open at about 170 degrees. I ended up not using it because the housing routed my lower house in a way I could not use. I found a different housing that actually uses standard Chevy thermostats and stuck a 180 in there and that works perfect. Enough rambling, I just wanted you to know that these thermostats can be manipulated. Also I believe in the later Gen IV motors they changed the design to have a more easily changed stat.

Pat