Define swap kit. Schumacher makes conversion mounts to let you put your 340 where a /6 was, but there are a bunch of other differences as well.

that would be the very most basic kit you could get.

When I converted my 72 Swinger from /6 to 360 I had to swap the radiator, the throttle cable, the transmission and kickdown, the exhaust, the radiator hoses, the AC hoses, all the accessories, probably could have just swap the mounts but the 360 came from a donor so it was dressed. some of the wires needed length adjustments.

I am probably missing a few other things, but this was back in 93 so it's been awhile and no one was making a kit nor was there a Moparts back then. I did my research, had everything on hand and the swap took me on day to do. I was fully prepped and probably had several days worth of prep done before the swap started.