b16>b18 lighter, less power

f20b>h22 heavier, more power

now becuase of R/S ratios i believe the f20b and the b16 are the better of their two respective categories, although they give less power they will make revs better but for 4k y ou are looking at the first category because it's easier and won't cost 5k for parts/install minimum like the others

 

k20 have alot of untaped potential. I'd recomend that.

 

k20, although a very nice motor, is not well suited for this application due to high costs.