I tracked my low mileage 1970 Swinger 340,4spd/3.55s in summer of 71. It went [email protected] on stock E70-14s.It scaled 3330 that day, car and driver. This translates to a W/P of 13.5 and so 247 hp. I wasn't the fastest or quickest 340 car around but the engine was very strong. And yes there was a lotta tirespin.
Your 96 translates similarly,but I think the 69 cars were a hair lighter.
96mph is a 14.4 W/P. So if car and driver were say 3250,then 3250/14.4=226hp. But if you had some junk in the trunk and scaled at 3450, then 3450/14.4=240hp.
The trap time is very little affected by anything except power,and weight,and at what horsepower you get into the window.
Your trap rpm with those little tires might be right on at 5260 in 4th.
Your weight might have been minimal.
So your 340 might be down some, but seems almost typical of the era.
If you did scale light at 3250, then I'd have to guess the low mph could have been Short-shifting.
I don't think lack of timing is worth 25hp; it woulda had to have been way off. But, might lack of secondaries be on the table?