There are a few scrap frames out there that still have the tank mounts. Now is a good time to ask around for donations. I did mine nine years ago with a kind contribution from a fellow member.
Hopefully you are a metal worker of some skill so you can mock up exact mount jigs that bolt to various points on the frame using angle iron, flat bar and small diameter tube. Then you can cut and shape the donors to lay alongside the tank tube for welding, grinding and polishing.
Those tortured looking lower tubes must have been coated in filler to cover the damage. There are craftsmen in England who specialize in retubing.
The more you can do yourself the better. And....that regulator mount must go