auto or M6 for a built engine??

i will be getting a LS1 to build it up a bit. it will be getting all new rods, steel crank, forged pistons, headwork, cam etc. i was wondering what would be better for me, a manual or auto? i know the manuals are harder on the rears, and most fast LS1's i see at the track are all autos. any input would be great.

2nd gear burned out for me at 19.4k miles, mines an stock A4 transmission. Usually the fast autos at the tracks have some aftermarket torque convertor.

i have read the the t56's are stronger than the autos. however, if i get a 6 speed, i think i will want a newer car with an updated clutch. also, i don't mind putting in a new convertor. i just mainly wanted to know if it would make more sense for the auto or m6. durability was the main issue for me trying to decide. thanks

a stock m6 is known to hold 650hp stock and 800 with the viper shift forks and input shaft........... :D