it will fit ok, all b series heads are interchangable, and b16 and b18c4 are the highest flowing of any b series, so its defo worth while if you ask me.
?? B18C4 is probably the lowest flowing head on B series Vtecs.
Putting a C4 head onto a B16B would be pointless and a downgrade. Even a standard B16a head is better flowing up in Vtec than a B18c4 head.
What motor do you have to start with?? Or how much of a motor do you have?
The c4 head is desirable for two reasons.
1) it has quench pads around its combustion chamber for smaller volume which will raise both the quality and quantity of compression.
2) it has a more direct shot of incoming air into the combustion chamber from the intake manifold. Depending on what your goals are, using the stock P 72 may be desirable or swapping to a skunk 2 will work well with proper tuning.
I would almost always choose this head over the standard PR 3 and even the factory ITR/CTR.