Thanks for that video, it clears a few things up for me. First thing I'd like to note is that based on your video, I'm pretty sure that the V6 6R80 is not what you want. That one will require you to cut the leg off the block. Performance Automatics makes an adapter for putting a V6 6R80 behind a 429-460 or an FE (both engine bolt patterns are in the adapter). I got my hands on one a while back, and put it up against the back of an FE block. In the picture below you can see that the leg of the block goes right where the starter needs to fit.

Performance Automatics specifies that you should use a 6R80 from a V6; their rationale was that the top two bolts for bolting the V8 version of the 6R80 onto the FE would interfere with the top two FE bellhousing bolts. So, the V6 version is what they want to use. But watching the video, I don't think that's what the kit shown in the video is using.
Bendtsen's kit looks like it uses a transmission that is not a V6. I'm guessing it's from a V8. Here's a picture from their video, followed by a picture of my V6 trans from about the same angle. Look at the difference between the locations for the starter on the transmissions:


Also, looking at their adapter plate that is bolted on the engine, the top two bolts for the transmission are very close to the top two FE bellhousing bolts, but they don't interfere. So, my guess is that they are using a V8 version of the 6R80. Greg, you should call them and find that out. If that is true, it would be great to know that it is available, it would save me the trouble of trying to fabricate one.
Here are some measurements from my transmission; I assume that the bulk of the transmission between V6 and V8 are the same, and only the bellhousing area is different:
Overall length: 26 1/2"
Width of the bellhousing at the input shaft centerline: 17"
Width of the pan: 13"
Width of the case 6" back from the bellhousing flange: 12"
Height of the case 6" back from the bellhousing flange: 5" over the transmission centerline
Width of the case 9" back from the bellhousing: 10 1/2"
Height of the case 9" back from the bellhousing flange: 4 1/2"" over the transmission centerline
Most of the rest of the trans is 10" wide, and 4" high over the transmission centerline.
Hope those measurements help - Jay