First time out in the 71 dart

Doing the math, 111.6 with 30 inch tires and 4.88s should be 6124rpm plus TC slip.If the tires grow the Rs will be less. If you are on the 6600 limiter then its 6600/6124=7.8% slip, or more.If the tires grow just 1%, the Rs should be 6063pus TC slip. Again if you are on the 6600 limiter, that would be 6600/6063=8.86%slip, or more
I would wonder about the chip. Or about the TC. What does your tack say?
What does the Dyno graph look like?

( rpm x tc )
---------------- = mph
1056 x R1 x R2

-Where tc is tire circumference, R1 is the diff ratio, and R2 is the trans gear,going over the line.
-tc is; 30 x 3.1416(pi) = 94.24inches