maybe I am over-thinking this-but
1) clearance the header for steering box
2) Small block mounts are right- everything is right, I would try a different 3 bolt mount- they are all the same, but manufactures are different, mine are cheapo ones and they fit great on the stands
3) is there any way to (run 'em home with an impact) I would only do this if there was 1/4 clearance- 1/2 is too excessive
hopes this helps
all your application stuff is right- i would just try a different 3 bolt mounts
DO NOT go with BBlk stands, just cause you other issues- Chris