ok just my 2 cents between K and B series
i have been experience with b16a,b16b,b18c R & b20b
the most cost effective for b series was going like this
get a b16b block re sleeve & stroke to 1.8(87.2mm storke) with 86 mm piston 12.5:1 CR(still maintain 1.6 series :))
GSR Head good port...