Slightly messy this way... Make sure truck is cold. Unbolt thermostat housing located on the top front of the motor, with the upper radiator hose attached to it. remove housing, remove thermostat. Clean gasket surfaces on intake manifold & thermostat housing. Spread gasket silicone on intake thermostat flange. Install new thermostat, install new gasket on top. Spread gasket silicone on underside of thermostat housing. Bolt housing on intake. Remove radiator cap & top off with 50/50 coolant/water.
yes.
will a 1995 Chevy 350 lt1 motor work in a 1990 Chevy pick up
Yes.
No spark.
NO.
As long as the 350 is a fuel injected engine / TBI / Throttle Body Injection engine there is NO difference.
41 to 47 psi.
6ft
yes
5 quarts with the oil filter.
YES, they are basically the same engines.
All Chevy small blocks and big blocks would "fit" into that 88 but, you will have to deal with fuel delivery.