They're discontinued from GM, but the part numbers are 10213125 L/H, 14039436 R/H. The stamping numbers on them are 334970 & 334971. IDK if it's accurate or not, but I've read stamping number 459021 will interchange. IDK if these fit, they look the same, but Summit has OER repop engine mount brackets for F-body cars:
Free Shipping - OER Engine Mounting Brackets with qualifying orders of $99. Shop Motor Mounts and Inserts at Summit Racing.
www.summitracing.com
Tommy