The way I read it... if you are going for a CFI in an airplane, the spin training has to be in an airplane.

(i) Accomplish the following for a flight instructor certificate with an airplane or a glider rating:
(1) Receive a logbook endorsement from an authorized instructor indicating that the applicant is competent and possesses instructional proficiency in stall awareness, spin entry, spins, and spin recovery procedures after providing the applicant with flight training in those training areas in an airplane or glider, as appropriate, that is certificated for spins;