These are adjustable motor mounts made for GM/Chevy engines on a vastly wide range of vehicles.
These universal engine mounts are designed for use on all types of four wheel drive and two wheel drive vehicles that have frame rail widths of up to 29.75”
To The engine mounts are adjustable from widths from 23.75” to 29.75”. The adjustable slots allow you to move the engine from one side or the other to allow for the above mentioned clearances.
Measure your frame width and set the frame brackets at a width just under that. As you lower the block into the frame rails and find the proper heighth and front to rear location. Clamp the frame bracket to the frame rail. Once the brackets are clamped , you can then adjust the side to side on the mounts.