Updated SPITFIRE HEADER INSTALL 63-66 A-body

Haven't heard anything about him in years.
For planning purposes, using Schumacher mounts, or any other brand, to install any small block in place of a six (six K-frame remains) or an eight (into eight K-frame) versus the OEM engine mounts on an eight replacing an eight, for header clearance purposes, does the engine end up being at the same spot from steering shaft and other engine bay components, etc, correct? I read through this old thread and I know there's hundreds of threads out there on headers being installed in early A's, maybe more recent threads for sure (than this Spitfire thread) on TTI's and even other brands installed into the early A's, I'm thinking if different motor mounts (brands) can make a small difference when this guy has to bend the header in this spot or that spot to get his to work when the next guy posting did not, etc. I guess what I'm asking, have people run across motor mount dimensional differences causing headers install differences (clearances)?