Identify the crossmember before you buy the LS mounts. QA1 7740-374 is the steel engine-mount kit for the specified QA1 C10 crossmember, not a shortcut for bolting an LS onto the factory crossmember.
Fitment
Manufacturer lists 1963-1987 C10 applications using the specified QA1 C10 crossmember and an LS engine.
Match the installed QA1 crossmember and engine-mount layout. Factory-crossmember, LT-engine and other engine-family applications are not claimed for this part.
Included
LS engine-mount kit with mounting hardware identified in the exact supplier record. The linked crossmember guide requires customer-supplied hardware to attach the engine plates to the engine; do not count those bolts as included.
Before ordering and installation
Check the engine, crossmember and driver/passenger mount orientation before installation. Use the engine-mount section of the linked crossmember guide; the two sides mirror each other.
Match and obtain the engine-plate-to-engine fasteners separately. The guide uses supplied carriage bolts behind the plates but specifies customer-supplied hardware for the engine attachment.
Mock up the engine and verify clearance for the installed oil pan, steering and surrounding components before final tightening. Follow the current crossmember guide for bushing assembly and mount hardware.
Manufacturer warning
WARNING: Cancer and Reproductive Harm. www.P65Warnings.ca.gov
Manufacturer product information and fitment
Manufacturer installation guide