Overdrive Options

Hey folks. I have a good thread on the T-56 Magnum conversion if you are interested. I also have some info I want to share on overdrives.
I built my 64 Valiant with a 5.2 magnum engine and A-518 from a 94 Dodge Ram truck. I used a new 3.91 SG Rear axle.
When I first completed the conversion.... Things worked properly, no diagnostic codes, etc.
I was a bit surprised with the performance. The car ran ok... Got 23 MPG... Everything seemed good. When I floored the throttle.... It would spin the tires some... And then rev and accelerate, but not like I had hoped. I swapped ECU's, got a great torque converter, while each of these helped.... It never cured the problem I felt.
I have many, many years of experience with good running Street small block Mopar engines. Nothing way radical, 340 CI, mid 12 to mid 11 sec. 1/4 mile. I realize that the 318 wouldn't be the same.... And the computer controlled the EFI..., it just didn't seem right.
SO....... I pulled the engine, ECU, wiring, etc. I had a 340 that I had ran many times at the race track... Running low 12's , low 11's with 100 HP NOS.
I kept the same torque converter, same 518 trans., same gear, etc.
It ran much better..... Much better.. But it didn't feel like my 68 barracuda (mid 12 sec. Street car).
I will cut to the chase. After asking many people about the problem, the only remaining area of possible trouble was the transmission. While everything on the transmission worked perfectly, the overdrive and the lockup functioned perfectly,.... The car still felt like it was towing a 3500 lb. trailer!!! I was devistated!!!
Since I had just pulled a wonderful 727 from my fathers 69 Cuda to install the T-56, it was just sitting on the floor. I decided to finally pull the suspected problem transmission, and replace it with this 727.
Once completed.... I got to take it out for a test drive today!!
I FOUND THE PROBLEM!!!! Wow!!!! Now this car runs like it is supposed to!!! Simply amazing!!!!!!
I have talked to several reputable transmission people, and they all tend to agree that the 518/500 take a huge amount of power to run. Now... An everyday driver... Might be ok, but it was a baffling disappointment for me.
If there are any questions that I can answer, please let me know. I hope this will be of some value to others. Thanks Todd.