the 3 isometry classes of irreducible [8,3,5]_4 codes are:

code no       1:
================
1 1 1 1 1 1 0 0
2 2 1 1 0 0 1 0
3 2 1 0 1 0 0 1
the automorphism group has order 4
and is strongly generated by the following 2 elements:
(
2 0 0 0 0 
0 2 0 0 0 
2 2 2 2 2 
0 0 0 0 2 
0 0 0 2 0 
, 1
, 
0 2 0 0 0 
2 0 0 0 0 
0 0 0 2 0 
0 0 2 0 0 
2 2 2 2 2 
, 0
)
acting on the columns of the generator matrix as follows (in order):
(3, 6)(4, 5), 
(1, 2)(3, 4)(5, 6)
orbits: { 1, 2 }, { 3, 6, 4, 5 }, { 7 }, { 8 }

code no       2:
================
1 1 1 1 1 1 0 0
2 2 1 1 0 0 1 0
2 1 2 0 1 0 0 1
the automorphism group has order 12
and is strongly generated by the following 3 elements:
(
2 0 0 0 0 
0 0 2 0 0 
0 2 0 0 0 
0 0 0 0 2 
0 0 0 2 0 
, 0
, 
0 0 0 2 0 
0 0 2 0 0 
2 2 2 2 2 
0 0 0 0 2 
2 0 0 0 0 
, 0
, 
1 1 1 1 1 
0 0 0 0 1 
0 0 0 1 0 
0 0 1 0 0 
0 1 0 0 0 
, 1
)
acting on the columns of the generator matrix as follows (in order):
(2, 3)(4, 5)(7, 8), 
(1, 5, 4)(2, 6, 3), 
(1, 6)(2, 5)(3, 4)
orbits: { 1, 4, 6, 5, 3, 2 }, { 7, 8 }

code no       3:
================
1 1 1 1 1 1 0 0
2 2 1 1 0 0 1 0
3 1 3 0 1 0 0 1
the automorphism group has order 48
and is strongly generated by the following 5 elements:
(
2 0 0 0 0 
0 0 2 0 0 
0 2 0 0 0 
0 0 0 0 2 
0 0 0 2 0 
, 1
, 
3 0 0 0 0 
0 0 0 0 1 
1 2 1 0 2 
0 0 1 0 0 
1 1 3 3 0 
, 0
, 
0 2 0 0 0 
2 0 0 0 0 
0 0 0 0 2 
2 2 2 2 2 
0 0 2 0 0 
, 1
, 
1 1 1 1 1 
0 0 0 0 1 
0 0 0 1 0 
0 0 1 0 0 
0 1 0 0 0 
, 1
, 
2 2 3 3 0 
0 0 0 3 0 
0 0 1 0 0 
0 3 0 0 0 
0 0 0 0 1 
, 1
)
acting on the columns of the generator matrix as follows (in order):
(2, 3)(4, 5)(7, 8), 
(2, 7, 5)(3, 4, 8), 
(1, 2)(3, 5)(4, 6), 
(1, 6)(2, 5)(3, 4), 
(1, 7)(2, 4)(6, 8)
orbits: { 1, 2, 6, 7, 3, 5, 4, 8 }