using a chevy hi-volume thermostat keeps the big Caddy running cooler than the stocker. you have to do to make it work is put a 1" softlug into the by-pass hole (after driiling a 1/8" hole to relieve any trapped air in it). worked great for me! There is no need for a by-pass on a hot rod!Do not use a Chevrolet thermostat in your Cadillac. You will have inefficient cooling. The Cad thermostat has a plunger closes a passage to then route coolant for most efficient cooling after a quick warmup.