Because the c5 and a k20 cost at LEAST $1,000 more and for what? 20-30 extra hp that can be achieved with bolt-ons? Not to mention if you wanted a C5 later, you could always save up and buy C5 parts they're interchangeable.
b18c1 - 175-180 hp
b18c5 - 190-200 hp
k20 - 210 hp (i believe)
Correct me if I'm wrong on any of these but I'm pretty sure they're close. And with my plans to boost, a b18c1 would be the best choice.
Actually since I'm kind of on the low-income side, I'd probably take a b16 before either of those with its 160-170 hp,
Specializing in JDM-USDM Engines & Parts...hmotorsonline.com sells the complete conversion for $2500.
Don't get me wrong, the b18c5 and k20 are both better motors no doubt about that. But when you compare dollar for dollar in the long run, the others win. C5 and K20 are best for al motor.