I don't know where you are going with this but I did notice something intersting:

GP volume = (440 rc)^2 x (280 rc)/3 = 18069333 rc^3

Since you want us to equate one volume dimension with 440 rc this whould mean that we come up with an erea length of:

A = GP volume / (440 rc) = (18069333 rc^3)/(440 rc) = 41066.7 rc^2

If we consider a square with this are then each side of the square is:

x = sqrt(A) = sqrt(41066.7 rc^2) = 202.649 rc = 106.098 m

mean Djedefre pyramid base length = 106.091 meters

Nice.