A stock thermostat is just fine, there is no need for a 180 thermostat. You are not gaining anything by having the engine run cooler and in fact if you want to get technical it could perform worse when the cylinder temps are less. If engines could run at 250 degrees and not melt other system down and have no other issue it would be more efficient. But that's not really ever going to happen.
So the stock 195 degree thermostat is just fine. Me personally I've jumped over the LS game for several years now and stock thermostat's are still the best option even on cars making 400-800hp and the only time people want something cooler is if they track the car.
The wix 1040 is the short filter and the 1036 is the longer filter. There is no fat filter that I know of. Though I'm sure something would screw on with the same thread pitch but sealing correctly on the oil filter housing is another story.
Anything longer than the 1036 will fit the subframe or lower control arm.
Probably go with a 5W40 or similar. Give the bearings a break in the winter with the 5W rating.
