Why do you want an engine conversion? If you're looking for an easy-ish one I'm doing a MK4 Escort with a Zetec Turbo conversion. It's cost me less than a grand so far and my engine is built with all the right bits. I used a de-compression plate instead of getting uprated pistons so I'll be limited to how much boost I can run but if you were to add pistons at 600 and ARP con rod bolts you could run it a bit higher. I'm probably looking at over 200bhp which isn't bad but with the pistons etc you could probably get 250bhp.