I imagine youll either have to fab your own pieces or make do with what you have. Unless you can find an NOS supplier who still has that stuff on the shelf???
Mine has these
bellhousing mounts which attach to a steel block surrounded by rubber (square in shape) and have bolts which both go from top and bottom into a threaded portion of the block. There are also 2 steel squares, 1/2" thick-ish, which sit in there somewhere to.
Both sides are different on mine and it tilts the engine an inch or so, to the passenger side. Dont know if thats how a Chevy is setup?
You can almost see what I mean about the tilt in
this pic here.Dont know if that helps or confuses you more!

Jeff