Ted, the fan should be centered [front/back] in the opening [
56 panel w/ 350, 1" spacer] and the usual shrouds will come real close ... if you need a bit of adjustment to get that positioning, the alloy spacers [up to about 2.5" I think] will do fine
with the original fan .... OTOH, the 55-57's had a factory arrangement that moved the rad back to the correct close space and you might be able to work that out from pics in the assembly manual
Bill
