Thanks for your comments (and PMs).
I'll take the wedge spacer out of the tank set up (which was meant to fix the problem!) and see how bad it is, but have no shims at all on the engine mounts - standard Ford FE. Probably going to have to cut the neck - beyond my skills set, but i do now a local hot rod welder. Hopefully he can help me. ...and then re-paint
I have never worked out how to upload pics in a post - always fails, 39kB limit seems crazy.