I don't think the C7s were used in any tractors, but the 3116 and 3126 are earlier models of the same family which were used in the 35-45-55 Challengers and some combines.    The C7 would bolt in in place of one of them, but you would have to do your own wiring.  Some of those engines appear to be missing fairly substantial components, but they are worth considerably more then the bids.  Thing about an auction, it's not over till it's over...the price will be determined in the last minutes.