I'd take the offer and negotiate it with the engine stand unless you want that as a decoration
It's condtion can be guessed pretty good on the stand by a compression test and just a look inside valve cover would tell a lot. With some tricks it could be started on the stand if whole.
There should be an orange sticker on the valve cover that tells you not just what family of engine it is but whether it's the 351 or 400 which otherwise look identical and I think would fit either for a replacement.
Again - I knew them and owned them myself in...... 1973 Full size Galaxie 500, 77 LTD, and a 79 Lincoln Continental Town Car. After that I think they were only used in the trucks. They are one of Ford's better engines IMO but not worth a fortune that I know of just sitting there like you said,
T
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Tom Greenleaf - MetroWest, Boston