I have a mk3 fiesta xr2i 16v (1.8 16v)

I want to do a 2.0 turbo conversion

Was going to use an st170 bottom end with a blacktop head.

What would the differences be between the 2 blocks? Would it be easier to fit different rods and pistons to a silvertop block and keep the silvertop head instead of a blacktop?

Cheers