I'd go with a 3000 stall lockup converter, like the TCI 432800. It is a great converter. I had one in my combo a few years ago. My combo was a stock '85 CFI 5.0 HO with the '86-93 exhaust. I would cut 2.0x 60fts with it and go around 14.9-15.00 @ 92/93 mph. I plan on running another TCI 432800 converter with my 347 combo. I should have it together soon.
I think going to a 3000 stall lockup converter now is a good choice, especially if you plan on future mods. Heads, intakes and/or a cam swap moves the torque peak up. The result will be a better matched converter next year. Since the converters locks up, the stall goes away in 3rd (or drive).
If the 3000 stall scares you, go with a 2500 unit. But if you plan more mods later, you'll wish you went slightly loose on the converter the first time. Just for the record, my stock '88 converter stalled around 2000-2100 rpm on the transbrake.
Be wary of any custom converter unless you can provide a dyno sheet. The converter guy needs to know the torque peak of the engine. That is, if you want a matched converter. Converters are a science, just like camshafts, and you NEED the proper specs to get the proper part(s).