Also, not that you're going down this path, but for others interested, the 250 is a doable swap. The issues to someone wanting to keep any of the older transmissions and a couple other things from the old setup make it costly. According to "the book" it's a little easier on the 64/5 Falcons.
You would have some advantages with a 250 (way more transmission options being the main one), but the swap isn't a easy as the 144/170/200 interchanges.
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