Hi guys, I've got a 2 ltd black top in a mk2 4 door - it produces around 150hp at the rear wheels so I am chasing around another 40 plus hp to give it some individual charactoristics. I am currently running twin 40 mm dcoe and had an opportunity to purchase a twin screw eaton supercharger complete with electrics - the more I pull the engine down to swap and change I have realised the engine with the supercharger is a silver top zetec. Can anyone shed some light on the differences from cylinder head and pully's and what I can use to convert the cerpent belt pully's to accommodate?

Some think that the ST has a stronger bottom end than the BT the ST doesn't have the under piston oil spray/cooler but a BT with Eagle rods and ARP studs may be the way to go. Depending on how the mighty dollars goin the US is the best place for performance parts, there is a mob that do a reverse impeller for the water pump I can't think of the name at the moment, someone will know I'm sure.
Are you road registered with the 40's? if so what state are you in? How hard was it to pass emissions? 

Silvertop zetec look like this. . Even tho mine is now orange top!

Blacktop looks like this. .

The main outside difference is the big cam belt idler pulley on the Silvertop and the oil pump is attached to the block.
Blacktop has the belt covered and runs 2x tension/aux pulleys and the oil filter screws directly to the motor. .. Same way a pinto does.
As for internal strength of either zetec.. The minimal thing to do is ARP bolts on the rods or go Eagle Rods to eliminate any weakness there. Pistons are Mahle to start with on blacktop which cope fine upto 250 bhp/7000. ARP the flywheel bolt too and dowel it while your there.
I bought a Jackson Racing supercharger and inlet from USA. ... which funny enough came from a '01 focus wagon as a optional extra from the dealer , haven't tried fitting it in a mk1 or mk2 yet. .
Cheers