WHY spend an extra money on a B18c5??? it never makes sense. you can build a GSR with the extra cash YOU saved by not buying the c5, and produce MORE power. who cares about the type-r head.... wow B16 ported head. you can buy a b16 head and port it and slap it on a GSR block... all the type-r motors ARE b16 ported head B18c bottom block. CTR is the same thing BUT 1.6 internals. So if you pull out the cams, and change the valves, and new pistons there goes your 2-3k down the drain.

Seriously:
If you plan to build a motor
B18c1 or work on the D16

If you plan not to build a motor
B18c5