The generator matrix

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

generates a code of length 68 over GR(64,4) who´s minimum homogenous weight is 460.

Homogenous weight enumerator: w(x)=1x^0+9632x^460+9520x^461+1512x^462+168x^463+21x^464+36960x^468+25536x^469+3304x^470+1008x^471+189x^472+47712x^476+29232x^477+2296x^478+2408x^479+294x^480+56224x^484+32480x^485+3640x^486+7x^520

The gray image is a code over GF(8) with n=544, k=6 and d=460.
This code was found by Heurico 1.16 in 13.4 seconds.