I have a 2001 SS with an LS1, 6 speed transmission. looking to maybe switch up to an automatic trans for drag racing. any ideas on what to put in it.

 

T-400 is a popular swap and with a few upgrades damn near bullet proof.
Is this going to be a track car only or street driven as well?
If you're doing a high stall convertor for hard launches with a big cam you'll want to upgrade the rear end as well especially if you plan on low butt gears.
Subframe connectors are a must have too.
I almost hate to see an '01 SS made into a strip can and the M-6 taken out,not a lot of these cars out there.
Mine is also an '01 SS M6 car.

 

i was thinking a t400 but still wanna drive it on street. maybe a 4l60 or 4l60e? something to handle 1200hp. gonna move to rear end after.

 

500 hp is pressing your luck with a stock rear end,1200 hp? not sue an OD trans like a 4L60 can be built for that much power.
If you're planning on that much power you better start at the rear and work your way forward and you'll need a different motor,the LS1 block will not hold up with that much boost. Basically for a 1200 hp build all you'll have left of the car is the body,pretty much everything else has to go.

 

well i am not looking for 1200 hp but maybe one day over 800. Want something that will hold up in the long run of the build. I have to start with the trans because its grinding in 2nd and reverse. next will be rear end

 

Well you kind of need to do the trans and rear along with a driveline and u-joint upgrade together as a package unless you want to do the driveline twice.
It's not a simple bolt in deal,you'll probably have to get the driveline customized for the T-400 and again for the rear end upgrade so better to do it all at once.
If I were you I'd just get the 6 speed rebuilt and make sure the clutch is good then save to do the buld you want to do,trying to piece meal it bit by bit is never a good idea.
On the upside if you get your 6 fixed when the time comes for your build you can get good money out of your stick and all related parts from the clutch to the rear end as a package for someone that wants to swap from an auto to a six speed in their f-body or for a hotrod build of some kind,they can use the pedals the shifter and all.

 

If the SS m6 is in decent shape then leave it as is. To truly hit 1200hp and be dependable you are going to have to replace everything and I mean everything from the radiator to the rear. I would not even use the aluminum LS1 block, I would track down a good cast iron block for anything over 800hp. You can buy a plain Z28 with a blown motor for about a 1000 bucks. heck even if you sell your SS m6 car you would be ahead, You could buy an SS automatic for less if you really wanted an SS. The second you pull that M6 out of that car the value will drop like a lead weight through water.