Positioning Vintage Air system - need help

[rgunlock]

Hi, I'm hoping that someone who has installed Vintage Air in a 73-87 can help me out. I've already shaved my firewall so have no reference holes to mount the under dash unit. I've got the block-off plate to mark the mounting holes, but I'm not sure where to position the plate in the first place. Does the placement in my picture look right?

If someone has the plate mounted and can post a picture, that would help. I've searched and looked through 12-15 threads but can't find one that shows this block-off plate.

Also, if you've done Vintage Air on a shaved firewall without drilling holes, I'd appreciate a description of how you mounted the under dash unit. I'd prefer that than running the bolts through the firewall.

Thanks in advance for your help