I have seen a first-gen Z with 325 width tires...it used to have some huge chevy motor...BBC I think. You can get enough tire as long as you have 17"-18" rims.
FI junky: how much do you have to spend on your drivetrain? if you want to make a 600hp L6 plan on spending $7xxx on the base motor easy...then extras for stuff you need for the motor...fuel cell, new fuel lines etc...
and if you do all that laying the motor over would be a decent idea to lower your CG and give you more room for turbo stuff...while you are at it...
You would probably rip the motor mounts apart the first time you drop teh clutch...lol. Motor plates are in order!
A Z32 tranny would probably work since stage 9 Z32s are around like 1000 horsepower...
Here is my dream "fully built" L series motor that would be up there in power...besides my signature...
LD28 block Laid WAY over
85mm modified, lightened, LD28 crank
89-90mm bore
balanced, lightened, polished everything...
forged pistons (duh!)
1_fast_Z's DOHC crossflow head
sequential turbos (first small turbo runs out of gas and then switches to a bigger turbo like a supra.)
aftermarket EFI (wolf 3D...)
driveline:
Dana 44 IRS w/ inboard brakes
Z32 tranny
so...how fast are you willing to spend? That above is well over $15k of stuff...lol and good for 650+ ponies...