The '68 FSM lists rad# 2898047 as standard equipment for a GTX 4spd. The size is not shown, however the parts book lists that part# as a 26".

My experience with 69-69 B bodies is that 440-4spd have 26" rads, not 22".

Also, a 3.23 axle does not seem correct for a 4spd car. According to the dealer data book (and my own experience), a 440-4spd would have the 3.54 Dana as standard equipment. An auto trans 440 would have the 3.23 as standard equipment. An auto car would also have the 22" rad (like you have) as standard equipment. Perhaps something has been changed?