i used ST internals into silvertop block as the engine went into mk3 escort and was much much more adaptable than the black top block.
u used the silvertop head for reasons i cant remember but after trying to use 3 different heads i settled on the origional silver top head with Auto inlet or exhaust cam fitted, i think it was due to the later cam timing pulleys not being in correct position with black top/ST top end and early silvertop block/crank?

cant remember 100% but at the time simply no combination would work except ST pistons/rods in a modded silvertop block and head assembly.

engine was on Dellorto 45`s, maby this made a difference at the time? memory serves me no ideas at this time.

Sean.