The generator matrix

 1  0  1  1  1  1  1  1
 0  1  1  a 3a^2+2 2a^2+3a+1 3a^2+2a+3 2a^2+3a+1
 0  0 2a^2+2  0  2  2 2a^2+2a 2a^2+2a+2
 0  0  0  2 2a^2+2 2a^2+2a+2 2a  2

generates a code of length 8 over GR(64,4) who´s minimum homogenous weight is 40.

Homogenous weight enumerator: w(x)=1x^0+392x^40+448x^42+588x^48+21504x^49+6272x^50+59080x^56+150528x^57+21952x^58+1379x^64

The gray image is a code over GF(8) with n=64, k=6 and d=40.
This code was found by Heurico 1.16 in 0.567 seconds.