Stock fitment:
B20A (single carb, not imported to USA) - A cam
B20B (dual carbs) - 'C' cam
B20E (early D-jet) - 'D' cam
B20F (later D-jet and K-jet) - 'D' and 'K' cams - at least I -think- earlier B20F's still used the 'D' cam, perhaps the swap accompanied K-jet?

A B20F may have a 'K' cam, but the differences between a 'D' and 'K' cam are exceedingly slight - you'd probably never notice the difference. They have identical lifts and just a touch less overlap - so they trade a little high end power for a little better low end emissions. Probably nothing you would ever notice driving around, just possibly with an exhaust gas sniffer. If choosing one for replacement, might as well go with the one slightly better, though.

The 'D' and 'K' cams are more performance oriented than the B20B's 'C' cam and especially the tractor-like B20A 'A' cam. Putting a 'bigger' cam with a stock head will just make the engine peakier, but produce little if any extra power up high where it should, and make it weaker down low. With head work a bigger cam can actually make more power up high, and make it worth your while to lose some low end torque.