I Was Sooooooo close to doing a LS3 Swap. I had all the brackets from Holley along with a spreadsheet almost complete. Then I had an epiphany everyone is doing an LS Swap, LS is corp. etc. etc. Of course you know all this, but For me I simply aborted the swap and Returned all the parts stockpile. I do still have the Complete EFI wet sump gas tank for when I do EFI.
I decided to go all out and build a Butler Performance Engine. Im not finished yet as it is still in final assembly, but should look stock. Plus I will preserve my matching 400 Engine and not worry about it failing.
I support you 100% its your Car! Not sure what parts you went with. I had all of the Holly/Hooker mounts and they were awesome quality.