I woulndt so much say that the convertor is ineffiecient but it convertor may be alowing you suspension to work or efficently meaning that you dont need as much speeed to run the same time.
Notice you saying that you have run 108 but you had a worse 60 or 300 foot time. The car had to run faster bc the suspension didnt work as well as before. I have seen cars pic up time and drop speed bcoz of this

 

At MOKAN Dragway. You should come down sometime when it warms up again. 115 I think but it was with my 6-speed.

www.mokandragway.com

 

Cool, ill have to try to make it down there a time or two.

 

Yeah just let me know when you are coming down. I would like to see the car in person

 

I'll let you know if I make it out there.