They sent a rubber GM one with the kit. I swapped it for another when I remade their cross member to clear the exhaust scallops of the torsion bar cross member better. They make different height GM mounts, might shim to height and check your transmission, driveshaft and pinion angle.
At the end of the day, it better and easier to make your own hoop and cross member, if you can. That old Holley one isn't that great. The newer swap stuff looks stronger and more thought out.
