D series: easiest swap (because it isn't much of one in the first place).
B series: good and relatively easy/cheap swap depending on which motor exactly.
F series: not too sure myself, talk to Diana Nam or other members with the knowledge,
H series: about as hard and expensive as a B series swap.
K series: harder/expensive swaps overall.
J series: good amount of custom work and probably one of the most expensive.
I'd personally recommend looking up what type of swaps people do and how much they spend. Are you going to be doing this swap yourself? If so it's always a good idea to jump into a B series swap if you aren't too experienced. Figure out how much money you want to dump, and then look for what engine and parts you need.