The 1969 BOSS 302's received a 7.35x14 space saver spare, the 1970 BOSS 302 received a F70x14 space saver spare. The 1971 BOSS 351 also received the F70x14 space saver spare. The 1969 BOSS 429 received a 7.74x14 space saver spare and the 1970 BOSS 429 received the F70x14 space saver spare. I would think the weight of the car was the reason the 1969 BOSS 429 received the larger 7.75x14 tire.