They are welded in. The weld to the subframe and frame rails that support the motor mounts and the floor pans... They are very much a pain to do. You need to properly support the front end of the car to make sure the car itself doesn't sag at the firewall... I did it in my garage with a cut off wheel, grinding wheel, and an air chisel. It took me about 3 days to do it... But caution, you migh need to do the floor pans and frame rails too... I would buy all three for each side, that way in case you cut threw one or more you won't be stuck. Hope this helps..
289 With 302 heads Bored .30= Edellbrock Performer RPM = Holley 650 Double Pump = Hooker Headers to Flowmaster 55's= 03 Billet Rims = Name a part... Its been replaced.