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I livs in da hood. Nah Mean........

ok I'll try to make an effort;)
First you need to set a power target:) "4cylinder nd turbocharge it or if not get the s50 swap with tranny?"it's always the same question... it's your choice. It's based on your target HP and how you drive the car, it's a personal preference. On another side if you want a daily driven 600whp monster you MUST to use the 6cyl... and if you want to hear the 6 cylinder sound you need to use that too:D
On the other side there is a 318is with 615 crank hp, but have a lot of work done and another with a good powerful 318is is user "Ludiagsm" on this forum, search his posts.
Don't bore the M42 over 86-86,5mm.
It can be stroked to 88mm with the M47 (E46 320d diesel engine) crank, but this needs some mods to be fitted.
Pistons need to be custom made under specification, but some pistons' makers have done other times m42 low CR pistons so they know the specs. Call builders like CP, JP, Wossner, Wiseco, Ross asking what you need.
If the car in object is E36 (as it should be reading that is from '94), Neukin have a bottom mount manifold for it at right price. I have it and it's bullet proof (not joking:D, but it weigth a bit) and it has great tig welds, life warranty against cracks! ->
http://www.turbogoods.com/neukinbmw318turbomanifold.aspxOtherwise if you want to risk there are crappy cheapy OBX turbo manifold for these engines, always speaking of bottom mount. 666fab.com made great top mount manifolds, but they cost A LOT of money.
if you want a premade internal kit here is it,
$2,299.95:
http://www.vacmotorsports.com/catalog/cp---arrow-m42-turbo-build-kit.htm
as every preassembled kit you can have the same thing for A LOT less money if you buy each item separately.
Eagle Rods are 330$(ebay), pistons are 600-650$, cometic MLS headgasket is 130$ (ebay), arp studs are 150$(ebay) ... do the math and
you can have the same things for at least 500$ less than the kit before, if not more...
Please post specific questions and target level, as the argument is so big with so many solutions that is impossible to tell the "right one " without knowing more:p
don't be scared about our comments about your language, another possible M42 turbo is always good

P.S. welcome to the forum;)