For a crate engine, stay away from the GM 350/290 #12499529. It is running a cam with very early exhaust valve opening (poor gas mileage), very late intake valve closure (poor dynamic compression with the 8:1 heads), and is a weak puller in the bottom half of the rpm range. It is not a very good setup. Don't ask me how I know.
The stock 350/260 crate engine #10067353 is a much better setup, is cheaper, and has a lot more torque where you need it.
Another option is to get the 350/260 #10067353 engine and re-cam it before you put it in. It will void the warranty, but there you go. GM does not run in their engines, so you don't need new lifters because they haven't bedded into the cam yet, and the 350/260 valve springs are the same ones that are on the 350/290, which has .450/.460 lift, so you don't need to replace the valve springs when re-camming either. Two cams that are great in this engine are the Comp 12-306-4 (available from Summit; Comp doesn't have it as standard product), which will give you more horsepower and torque across the range and pull hard to the redline (5100 rpm), and the Comp 12-300-4, which will give you a ton of torque in the bottom half of the rpm range, pull very hard to 4000 rpm, and then run out of breath about 4600 rpm.
Another option is to buy the Vortec engine #12530282. You can put a regular distributor and carb+intake setup on it (rather than the ECM and TBI, which is a lot more fitment with your existing wiring harness).
Any of these would be easy jobs and won't break the bank. I would use a stock 1400-1500 rpm stall speed torque converter with any of these engines. They have plenty of torque in the bottom end and that makes them nice drivers for street use.
You can compare and contrast the torque curves of the 12-300-4 and 12-306-4 cams here. The 12-306-4 has the later peaks, but the 12-300-4 surpasses it in torque and hp below 3100 rpm, which is where you will do most of your driving. 12-300-4 also gets better mileage, with it's later exhaust valve opening.
http://users.rcn.com/weyand/smalls/300-306.jpgAnyway, probably more than you wanted to know, but I have just been through all this with a fine-tooth comb. My 350/290 is getting a new 12-300-4 cam this week.