‘It depends’ would be my answer. I’d really want to see it to get an idea of how it’s likely to fit together.

Firstly, what type of neck have you bought?

There are ‘true’ baritone necks with the same number of frets as the original guitar, to fit bodies where the bridge and pickups have been moved back compared to the standard guitar, so the extra scale length is shared between the neck and the body. That’s what the kit has.

Then there are ‘conversion’ necks designed to fit standard guitar bodies where all the extra length is in the neck. These normally have one or two extra frets compared to normal. If you try to fit that sort of neck on a baritone body, then the scale length won’t be correct; it will be too long and it won’t play in tune except on the open strings.