As you know 11.47 will get you kicked off most sanctioned 1/4 mile tracks, after a warning of course, cage time.
Trap mph is a good indicator of horsepower, ET is a good indicator of how the car does in the first 100', one tenth in the 60' can net 2 tenths at the big end.
Mid 11s hauling 3500 lbs is 500 flywheel give or take 50 hp, a zillion variables, but a good guess. Adding another 250 with a shot pumps that to 750.The mph is going to go up a little, yea, right, could get into the 130 if everything goes right. So R&P choice becomes important, tire diameter, converter choice also.
Not being really a drag racer, just someone who use the track to gauge engine performance. Usually made the trip to the track a couple times a year just to legally do 120, in 4th gear. If the trap mph stays in the 112 -114 range the 15 year old build is still healthy. Best 60's were 1.7s on the QTP, granny shifting 12 teens at 114. Tried the M/T drag radials, gave them away to a friend, couldn't hook them with the clutch I had in the car. As with most motorsports tires are important.
Next time at the track have the car scaled "as raced", you, sitting at the line. Important to know weight to make calculated guesses at mph, ET, hp, trap rpm,
At the track watch other car that are running mid 10s to 12 second range and look at their mph, the way they 60', are they doing those ETs on hp or are the 330's that good.
By the way, what rear are you getting built?