hi mate first of all the silver top has much bigger main bearing cap so it the best bottom end , but the black top has a sligthly better flowing head and the st170 even better. i would personally say that the black top engine would be the way to go as they are widly available , have a baffled sump as standard but you would have to make custom engine mounts. if you start swapping heads you have to start custom mounting pulleys etc so it aint worth the trouble. your from lincoln which is a shame as the best zetec tuner in the business has just finished and hes not doing engine builds anymore but he is still selling components. speak to ian howell at area six on tech@fiestafrenzy.co.uk he is a very helpful guy.

first you need to tap the back of the block for the breathers ports , here in the pics





you want arias pistons and eagle rod package pm me and i will have a word if you cant talk to ian via email . the compression ratio you need is 7:45:1 , a rebore of the block to 2.1 litres all new bearings etc. you will need a new 2.0 oil pump , a 1.8 zetec water pump , arp head bolts , 2.0 multi layer metal headgasket as these are the same as the wrc items but make sure its a genuine gasket and on the head side you just need uprated valve springs for some decent boost max 20psi , an rs1800 high output manifold and a decent set of injectors/ new fuel pump/ fuel pressure reg and an escort rs turbo exhaust manifold . at this stage you should use pectel engine management as reliabity usally comes and causes people major running issues. at this stage on a t34 turbo running about 20psi you should see a genuine 300bhp
after this , this is where it starts getting very expensive , custom inlet manifold , big throttle body , 650cc injectors , 3 bar map sensor , fuel pressure reg , big valve cylinder head with double valve springs and custom cams, venier pulleys , tubular exhaust manifold , gt30/ t61 turbo , external wastegate , with all this you should see 500+bhp @ 30psi but at this stage of tune you should have the engine put on the engine dyno to test each component.
your looking at the best part of £10,500 for all this mate



it all depends on how much bhp you want and how deep your pockets are!
to be honest you need to build the bottom end and then add to it as you want to as thats what i did.
hope this helps and let me know if you need any help
cheers paul