When you chose a converter keep in mind all the important items, but one of the most important is gear ratio at the rear, and first gear ratio in the transmission. But if you want it all, a big engine with a 2.73 rear axle then you can't have a high stall converter even if it is a lockup. Figure your engine rpm at cruise speed. This rpm should be in the power curve of your cam or you will never get any efficiency, even if the engine is turning slowly, because it is running at an inefficient level. The next thing is that the stall speed has got to be less than or equal to the cruise rpm. If the stall speed is higher then the converter won't be a good fluid coupling and will make heat like a furnace and cause trans overheating.
If you have a street converter it is most likely a flash converter. These only attain their listed stall speed when launched from a low engine rpm. But power braking for stall is much lower than flash stall. An example is in my truck I run a 3500 flash stall street/strip converter, which stalls at 3500 when I stab it. But when I power brake it the stall is about 2600. With 4.10's, a 25" tall tire, the engine runs just a little over 2800@70mph. That works. But I also have lockup, which brings it down to 2600, which gets me just at the bottom end of where the cam starts to work. So I get pretty good mileage and the trans runs cool. Don't give up gear for mileage until you crunch the numbers. You might be going backwards, especially in the power to the wheel department. Run as much as you can stand to guarantee the fun meter goes high.