spool type K frame

The V8 torsion bars are likely bigger than your /6 bars, unless maybe it was a non-AC 318 car and an AC /6 car, they'd be the same in that case. Either way, these cars were massively undersprung from the factory, so new torsion bars would go a long way to improving ride and handling.

The 340 will use a different driver's side mount than the 318 does, you can either use a spacer, modify the 318 mount, or track down a 340/360 mount. It's not a big deal.

The sway bar needs to be matched to the K frame. They're different depending on whether they're 67-72 or 73-76, the 73-76 bar routes through the K frame and uses sway bar mounting tabs that are in a different spot on the LCA. The non-sway bar LCA's are the same though.