have a search around the forums mate, there have been many conversions done in a simmilar fashion,
im assuming its a MS112 crown, diff will handle the power,
bolt in a 7mgte motor (can use the original mounts and sump off the 5m)
manual conversion. may need a custom tailshaft and gearbox crossmember, clutch master/slave cylinder and lines (id assume the 86 is auto!)
wiring,
fuel pump/s
intercooler
brake upgrade if you want it to stop
+ all the little bits and pieces that all add up during a conversion.
just buy some decent bridgestone/yoko....any reputable brand road tyre.
search, search and search these forums, you will find ALOT of information on the M series motors.
edit, and whatever your budget is, double it.
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