I have no problems with Gear Vendors, but you can probably put an AOD in there for a lot less money and hassle. Either way you have to deal with mounts and driveline.
Gear Vendors is local to me. I've been in their shop a few times. They make a good product and stand behind it. I am in the middle of putting a 4R70W in my 62 Falcon. I chose this route because the 4R70W is way more available than an AOD. Yes I had to buy a controller, BEControls.com, but I'm still less than the Gear Vendor, and I can "tune" the tranny. The 4R70W with a SBF pattern can be found behind almost every 3.8 V6