Here's a couple choices I know work. For torque, you don't really need a lot of compression, so you can cam it for torque and save money on heads, or you can go whole hog if you want to make it a land missile. I still have most of the parameters in the Comp Cams simulator from recamming my 350/290, so here's some data.
Maximum torque with minimum cash: Comp Cams 12-300-4CL kit (cam and lifters). This is what I did with my 350/290. .390 lift, so I didn't even change from the stock springs. Simulation says 275hp@4000, 422lbft@2500. Torque coming off of idle: 320lbft@1000. This is a great driver, with huge torque off the line and a hard pull to 4000 rpm, then it falls off. I guess. Don't know. 4000 rpm isn't where I drive. I diddled the governor on the TH350 with one size heavier weight on one side to move the WOT shifts down 500 rpm so it would catch an earlier shift and not wind out over the top of the horsepower curve.
Good torque, more horsepower up top, a bit more cash: Comp Cams 12-234-2CL kit (cam and lifters) plus recommended springs. This is the XE256H, which is what I think you meant. Simulation says 302hp@4500, 415lbft@2500. Torque coming off idle: 280lbft@1000. A bit softer on the start than the 12-300-4, but pulls hard to 4500.
Big money on heads, but wow on the top end: Comp Cams 12-234-2CL kit (cam and lifters) with Dart 127121 64cc heads. Same cam, with 9.5:1 aluminum heads with oversize valves; horsepower is all about getting fuel through the engine, so the oversize valves matter a lot. Putting the actual flow data into the simulation, I get 392hp@5500 and 436lbft@2500, with the same 280lbft@1000 coming off idle as the low-compression heads. Note how the higher-compression heads help with horsepower up top, but the low-compression heads are in the same ballpark with delivering torque in the bottom half of the rpm range.
So all of these are in the 280-320lbft range coming off idle, and 415-436lbft range at 2500 (which is nice and low, which is what you want in a street machine). All will work well with a stock stall speed torque converter, so that's easier on the tranny than a high stall speed torque converter for a motor with less torque in the bottom, and easier and more fun to drive around town. The difference is, do you want a hard pull to 4000rpm, 4500rpm, or 5500rpm, and what are you willing to pay for it? They will all drive about the same to 3500rpm, which is where the dyno curves start to separate.
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