He's talking about the thermostat flange in the original post. The Edelbrock 2176 has a dual bolt pattern for the
thermostat:
View attachment 1716042351
One pattern fits the 1977-older large-diameter thermostat/housing found on most of our cars, while the other is for the 1978 and newer smaller (Chevy) thermostat and housing. The later parts are required to clear the axial AC compressor used on 1978-92 LA engines. To my knowledge, the 2176 is still the only aftermarket intake that can be used with the factory '78-'92 LA AC installation. Some lack the mounting points for the compressor while others have runners that won't clear it.
The biggest issue is making sure you order the thermostat and housing for the
same year of car/engine. There's no way to make the "classic" thermostat work with the later housing or vise-versa.
