odd question for you guys c5 /c6 vette???

I bought some motor mount brackets to use in my ls1 rx7 , I thought they were c5 mounts but are in fact c6 mounts. they seem to be very similar in the mounting points and angle but the shape and look of them is different.my question is their interchangeability, can anyone shine some light on this for me? I've been on google like 12 hrs now. I know the gto uses one side C5 mount and one specific mount , other than that i'm unsure of what to try to compare them to, a coworker has a C5 and visually they seem to mount the same ...IDK.

top are the ones you have and bottom are c5?

mount holes all look in the same position, they just look beefier.

i have the bottom ones....

why not just get something like this:

LS swap mount kit

or get some poly small block Chevy mounts and make an adapter out of a couple of pieces of 1/4" steel and fire up the welder to make some frame stands to put the engine where you want it?

i'm using bits from here, and you can use the c5 pedestal mounts ....

http://www.roninspeedworks.com/powertrain/