What he said mostly.

2wd and 4wd tin grilles do have different front cross members for suspension but they use the same mounts. They all have 2 sets of mount holes - small block, big block. Shiney mounts in first pic are big block, the hole in one of them being for the oil pump. Used ones look like small block and IIRC 318/360 use the same on one side, different on the other. there is a pdf of the 78-81 truck parts book somewhere on the net.