What year are theses drums? Also are those cracks on the outside in the picture shown supposed to be there? They are in the inside and out... should i weld them shut and if they are supposed to be there can they be welded up and not hurt anything?
IF they are early Fords they are 40-41. Yes the slits beong there, no I wouldn't weld them up. They are likely an early "solution" to the brake dust problem.
Those aren't "cracks"-they're "slots". They are intentional but I believe the purpose is to show when the drum is oversize on the I.D. Check the diameter (inside). If it's over 12.060" the drum is suspect.