bb motor swap

[byrd32]

i own a 72 c10 that had a sb and am putting a bb in it. I've taken it and the weak single bolt through the middle motor mounts out along with the chairs (frame mounts). I have purchased a set (from junk yard) of 1970 c10 402 frame mounts.. they bolt right up to the cross member and frame.... but there's four bolt holes on there (just wait).
when i go and purchase the motor mounts from the parts store - they're pretty standard - the three bolts holes fit the motor then there's a large rubber pad and a hole on each side where the 5" bolt goes through running front to back once the motor is set in the truck... well what i can't find anywhere is the part that bolts to the frame mount and accepts the motor mount w. the 5" bolt. Anyone have any suggestions as to who has a schematic of this or who manufactures it now? as chevrolet has discontinued manufacture of the lower vintage assemblies. (btw - and no classic and the regular parts guys don't have or barely know what i'm even talking about) (and it's not a hybrid system like the 76 models w/ bb's that use the new mounts with the old plates)