K member swap

The 68+ idler arm is a better design that the 67 arm, so if you wind up with a latter model k-member that is a good thing.

Up through 72 the motor mounts were two plates of steel with rubber bonded in between. If the rubber bond failed (which it did from time to time) the motor could flop around and damage other parts. In 73 they changed to what is refered to as the spool mount. The engine mount has a tube of steel on it with a rubber insert inside it. The k-member has two ears per side that the tube fits into and a bolt pases through front to rear. Failure of the rubber will not allow the engine to flop around. That is why they are considered to be a better design. But there are now after market mounts for the older style that have metal that interlocks and if the rubber was to fail the engine is contained. If you use them it's just as good as the spool mount system.

The \6 torsion bars are not really strong enough for even the \6 compared to what folks expect from a car today. I would recomend that you go with the .890" diameter big block bars with the small block v8. Nice firm tight ride that is not at all harsh.

The 72 an older disk brake set up for an A-body is scarce and parts are hard to come by. Most folks search out 73+ A-body disk brake set ups. All the parts are still available at the local parts store and they are relatively cheap. But in 73 mopar consolidated on a larger upper ball joint across all lines. So you will need the upper control arm from the doner car as well as the disk brake spindle and caliper mounting bracket. Likely you will be purchasing new rotors but grab the calipers and master cylinder to use as cores for rebuilt items. The lower ball joint on the disk brake car has larger mounting holes for the spindle than drum cars but otherwise is the same (you could drill out the drum lower ball joint to accept the larger bolt). It does not matter whether the disk brakes come from a \6 or v8 car they are the same.

In 73 the idler arm, pitman arm and center link changed. Either vintage can be used you just have to use all three from the same vintage. The difference is how the stud on the pitman and idler mount to the center link. Also, contrary to what you may have heard starting in 67 there is no difference between a \6 center link and a v8 center link (there was prior to 67).

Whether you go with after market mounts or get a different k-member should be driven by availability and price, there is not real functional advantage one way or the other. When I did the disk brake and v8 swap I was fortunate that I was able to pick up a complete 73 v8 Dart with disk brakes for nothing. Stripped all the parts I wanted or could sell and sent the rest of the rusted hulk to the junk yard.