383 Rev Limit question

I appreciate all the help, I will be pulling the engine in two weeks to have the car painted at that time i am pulling the heads to see what has been done. I dont even know if the pistons are over sized or std. I dont know if they are flat top, dome, dish, any thing. I know it runs very well and seems to be very quick. I expected less low end quickness from a big block. Comparing to my chevy an 86 Monte Carlo SS with a 350 pushing 450hp and running 4:11 gears, the duster seems to be quicker with 3.89 gears and it has a ford 9" rear.

when I pull the heads I will take photos and post them just so you can see what I am working with. I cant figure the CR because I dont know whats under the heads. It would be ideal to run pump fuel instead of $8 a gallon race fuel. Not knowing the CR i dont want to risk putting pump fuel in when I was told to runn 11 or 110 by previous owner.