expert advice needed about my numbers matching automatic 727 torque flyle trans.

First off I doubt it's the converter causing the problem of winding up like you described, unless it's doing it in all gears (reverse included) but you didn't say that, you only said "in first gear". In manual low first gear the rear band applies and keeps things from freewheeling when you let of the gas. It sounds like a low band or servo (that's what applies the band) problem. Or it could be as simple as the trans. is low on fluid. any of those things will cause it to freewheel.

Let's explain the reason you see different versions of the same converter. First there's the converter for the internally balanced engine. It has no extra weights other than the weights all converters have to balance themselves. Then you have a converter for a 360 (externally balanced engine) and you also have a converter for a 440 externally balanced engine that requires a different amount of balance weight. There are also more converters for even more externally balanced engines but it'd take a lot of typing to list them all so I think you get the drift. Then you have converters for different year transmissions. Namely 67 on back and 68 and up. You have the most common converter used, a 68 and up 727 for an internally balanced engine (no extra balance weights).

The whining may also be a low fluid issue. Are you checking the fluid with the transmission in neutral? If not you should be cause that's the way they are made. That might be the whole problem cause low fluid level can cause whining and kicking in and out of gear. Only problem is if you ran it low on fluid long the trans. is probably toast and needs rebuilt.

BTW: My car is also a 68 Cuda fastback that had a factory 318 (has a 360 now), 727 trans. and a 8-3/4 sure grip. It's very odd to see the 727 and sure grip rear behind a 2 barrel 318 but now we know there were at least 2 of them made.