Modification of K-member idler arm mount advice

No help, but following. :popcorn:
Big surprise.

The double shear mount was a huge improvement and is absolutely worth transferring over.
First up, take several precise measurements from several points on the LEFT to the double shear (black) idler mount. Record them. Take numerous pictures. Save them. I'm talking centerline from the steering box mounting bolts to the edge of the idler mount, the holes for the through bolt, the flanges, everything that makes sense. Make note of how much the tabs on the idler mount lay over the K member where they are welded. Now using a series of grinder discs and maybe even thin blades on a Sawzall, remove the '67 Idler from the red K member and then the '68 and later unit from the bent one.
Clean all leftover welds from the red K member.
Take the '68 idler mount and place it on the red K. Position it so that it's placement matches the measurements that you have recorded. You can temporarily fasten it using am 1/8" drill bit followed by self tapping screws. Continue to recheck the measurements and adjust as necessary. MIG weld the tabs an inch at a time, alternating where you weld. It may not matter, but I'd not do continuous welds just to avoid the risk of things moving around with the heat. Once the welds are complete, I'd dress any sloppy welds with a grinder fitted with a sandpaper flapper disc.
The key to duplicating the placement is the measurements. Be thorough and accurate and you'll be as close to stock as any hobbyist can be.
EDIT:
I just saw the Jig/bracket that (MoparMatt?) made. That is an excellent tool that IF you had one, it would make things faster.
Everyone I know has a measuring tape though, so taking measurements is probably within your ability and costs nothing. Good luck.