I was under the impression that a t5-z was rated at 330 ft/lbs. Seems to me the beast that lives between your shock towers will make short work of that. Then again, you hear stories of people turning 11s with stock t5s all the time without any problems.
Like you, i just blew up a stock t5 (i did it w/@325hp 302). I replaced it with a t5z because the cost is easily less than half that of a tko once you consider: $2K+ for the tranny,new bell housing, new clutch disc, probly have to modify the drivehaft, and cutting the tunnel to fit a tko sounds like a real hassle too. Might even have to buy new crossmember (?) and carpet. Whereas you are already set up for the t5-z.
Having already replaced mine with a z trans, i can tell you that the 2.95 1st gear and .63 overdrive made a BIG difference. 1st now goes further thru the intersection than before, and lands you into the sweet spot in second. Barking 2nd is easy as
pie now. I still havent decided if i like the taller overdrive yet. My car (68 convertible) still has the original 2.73 gears, and needs lower gearing bad. I picked up a 3.50 posi for it yesterday but haven't bolted it in yet. With my 17" wheels and 3.50s i figure it'll be doing @70 at 2000rpm in overdrive. I'm building mine just to wring it out and maybe take a few road trips. You'd think that 3.73 would put you @ 2250 or so at 70mph - still running on the primaries toolin down the interstate at the speed limit.
One thing that i DO NOT like about the z trans, is the notchy shifting! When i first forced it into gear i thought it was defective. It is a whole lot better now, after @500 mile of break in than before, but still notchy as hell.
With my set-up a z trans made sense. With your horsepower the decsion gets tougher to make. I say go with the tko. Any old fool can restore an antique, but it takes a real man to cut one up! If you are like me, you'll only miss the money when you are signing the check, and you'll forget all about it when you are busting donuts is 2nd gear without worrying about breaking somthing. Then again,... you might wonder what the hell you were thinking when your interior is gutted and you're looking for a sharper sawzall blade to hack thru your floorpan with...