Minimal cost would involve keeping the 16v head which does not require the additional costs involved of machining to allow fitting. The 16v head flows far more than the 8v head.. it has to be a pretty special 8v head to make it worth considering junking the 16valver imho.

For me there are only two choices, zetec or CVH.. not a bastardisation of these engines, its worth remembering that the fastest Escorts in the UK at this time are still powered by a CVH

Getting decent reliable power out of any engine costs money and the reality is how fast can you afford to go. I would not use standard rods on a CVH, ZVH, or Zetec above 250bhp