cyl head

[willy wagon]

i got the cyl head off super major. i checked the casting nos on the head except for one prefex they the same. the heads look the same etc. one was supposedly rebuilt. i would like to go with that one. when were there head head changes? and what do i watch for? if the head has been machined will it be ok. i do not know who rebuilt the head it came with another tractor, with spare parts.