you said the trunk was full of tools, jack etc., so, without knowing the cars actual weight, and the actual air conditions (you can be at sea level and have 3500' DA) it's hard to say if that is a time representative of a 5.0 with intake/exhaust mods or not. My intitail thoughts are that it's slow but, you are throwing used parts together with unknown mileage/wear/condition...
Mine ran 100mph when it was stock with offroad H pipe and 3.73's, but it was essentially a new car at the time with an empty trunk and it had certainly never been on fire... and we typically had DA of 300' or better.
I really enjoyed reading this entire thread.
You have more guts than me, I would not have the "balls" to build a motor out in the yard like that... so if it were my car, it would be sitting and rotting.
So, all I can say is I commend you for your efforts and for actually getting out to the track and running it.
I have a lot of respect for guys that make do with what they have, and run their cars.
Tip of the hat to you young man.