Oddly enough the 308-328 where the most popular of the ferraris from 1976 to 1989, but only a few kits where made in 1/24-25 , here are the ones I made:
Monogram made a 308 GTS in 1/24 in the late 70's, easy to build & pretty decent kit.
Revell US made the Magnum 308 GTB in the early 80's, the same kit was marketed by sister Co. Revell germany as a Pionner sponsered rally car in the mid 80's. decent kits
but a few alignment problems here & there.
Gunze Sangyo made a really nice 76' 308 GTB (closed top) version in 1/24 scale, I remember buying it back in 1984, the beautiful artbox caught my attention , the kit was a typical Japanese motorized curbside kit, but with a few nice details, like opening doors, nice interior, popping headlights, opening engine cover & basic engine cylinder head, to cover the electric motor, the proportion of the body design was excellent. The kit was also boxed by Testors in 1986 for the US & Canadian markets.
Hasegawa also made a very nice 328 GTS in the late 80's in 1/24, surely the nicest of the kits available with accurate chassis & engine details, nice artbox, but this one is a late 328 not a 308
All of these are available on ebay, the Gunze 308 GTB is surely the rarest & most expensive to get even in the Testors box. hope this helps.