Engine? $200 or so, not all that desirable, even to other 2.3/Mustang II guys, and they're a dime-a-dozen, Ford probably built over a billion of them around the world.
Transmission? $150 or so, the C3 2.3
tranny is getting harder to find, but it's never been a highly sought-after piece.
I've got two 2.3s, a 2.3L 4spd, and over 100 other parts posted for sale as a group on a classified site for $600... this is a CRAPLOAD of 2.3 parts, including some one-offs, rare parts, and trick pieces, and no responses...
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1976 Ford Mustang II Ghia: 302 with a 600cfm Edelbrock carb, Edelbrock Performer 289 intake, Dynomax Blackjack headers, 2.5" exhaust with Flowmaster Super 44s. RJS 11-gallon fuel cell, C4
tranny, chrome 16" pony wheels, fuzzy dice, brown vinyl half-top, and painted in the tackiest color ever (harvest gold, that's why I call it "The Goldenrod").
Also have a 2003 Dodge Ram (lightly modded daily driver/tow rig/office/dining room/home away from home/workshop... I call it "The Big Blue Dawg".)