If the 86 is complete and not in bad shape other than maybe rust or bad paint, you'll have a good stockpile of spares. It might only need fresh fluids, a battery and a once over on the brakes (and probably a monster clean...) For $500 you can't go wrong, even for a junker. The 2.0 and 2.6 won't be interchangeable - 2 different transmission mounting patterns so bear that in mind. IMO 1/4" alloy for a reinforced trans sump is too thin. It should be at least 1/2" thick billet plate for rigidity.