What all will need to be replaced on the drivetrain to be able to handle 400HP? Tranny obviously and prolly the rear end right? anything else?

You definitely must change the trans, but the rear end may serve. How are you going to be making the 400 horses? High-revving 327 with an automatic? the stock rear will certainly live behind that. 454 with a TKO600 or T56? Your stock rear won't survive that.

383 mild cam and will be using T-56...will the rear handle that? Also will be driven quite a bit and will be ran kind of often(in other words not going to be a weekend cruiser, more along the lines of a street beast that goes to the track once in a while

not nessesarily needing 400 HP just end up building whatever it takes to get low 12's

The LSx guys with T56s tend to break their 7.625" rears before they get into the 11s, And aside from the Zexel torsen failures, the next most common failure is the gearsets rather than the axles. ( with rear-end girdles and drag radials)

Dont worry too much about the rear.... Unless youre running slicks you'll be ok.

SUBFRAME CONNECTORS!!!! You definately need those, or else count on squeaks, and ticks getting worse as months go by, maybe even a cracked windshield.

Also, iwould either invest in a good radiator, or at the very least some aftermarket Dual electric fans.

Other than that you should be ok.

k thanks

stock 91-92 Lb9/L98 fbody radiator with L98 dual fans will keep it cool. My car was fine with my stock radiator which i believe is the same as the 91-92 rads. Mine was a 89 Irocz, i just had the stock rad flushed out and checked for leaks.

Rear may hold ok unless you beat on it with clutch drops and such and/or add sticky tires

stock good condition T56 will last just fine. If you wanted to do alot of aggressive shifting you may want to upgrade to billet keys/etc for abit more reliability. Its just a basic upgrade rebuild. Not necessary tho

Just to add to that;

WHen i said rad/dual fans, its because my rad isnt enough SOMETIMES.

I have an air dam on my car, and i almost never use my fan. But in bumper to bumper, after about 10 mins, the single fan cant keep up, and it slowly overheats.

If you plan to do aggressive shifts, invest in a shifter with bump stops as well.

Also to add, i have 170 degree stat and fans programmed to turn on at 180 off at 170 or w/e it was. IF the fans didnt come on, in traffic in the summer it would start to get hot but even just 1 fan on it never got above 185. Both fans kept it cooler