1991 Chevy Camaro engine help

Hi this is eric and I am about to kill my camaro. Lately I have been getting obscene amounts of white smoke coming out of my pipes and the new thermostat its going nuts, jumping in temp as soon as the car warms up. Also the ol pressure is jumping around I have a new gauge and it says it runs from 40 psi to 80psi but sits mostly at 60psi. It is a chevy 350 v-8 out of a silverado and has numerous upgrades including a comp cam kit, keith black forged aluminum pistons, msd ignition, accel distributor, aluminum heads, edlebrock 600cfm four-barrel, and steel crank. Also power sterring is out and am wondering if this is a cracked head gasket or worse one of my aluminum heads is cracked. By the way this is a throttle body. Thanks a lot you might just save my camaros life