A ST-10 in good servicable shape will handle about 600 hp max, 525 ft.lbs. Might get it to hold more if you send it out and have high nickel gears and pro-shifter syncronizers($1500+) put in. Secret to making it live is a clutch that slips a controlled amount(like the McCleod Sof-Lok $1200+) and tires that will slip. They are the fuse that blows before the tranny does.
1000 hp... you are strictly in the area of Lenco, Liberty, or G-Force ProStock and Pro Mod trans territory. You will have $8,000 plus between the crank flange and the rear end, it ain't cheap.
Is this for the now famous 1000 HP stock block
Pontiac from another thread??