The 72 D100 Dog.....

That's a beautiful truck, it looks like a fun ride for sure!
The times are pretty impressive for what it is IMHO.
I have a few questions:

What is the weight of the truck?
What RPM did you shift at?
What was the MPH that you were getting through the traps?

I bet with more gear (say 4:10s) and a sure grip with say about a 3,000 stall converter you could easily drop half a second or more off of your E.T. and maybe a full second with some driving experience and tuning.........

BTW, the truck is about as aerodynamic as a brick as well as light on the back end, so traction might be a big issue as you hop it up more, but enjoy!