[ford38v8]

Gary, I hear tell, (no experience myself) that a 9" is overkill for a flathead, an 8" being more appropriate. Perhaps a comparison of options here would benefit your goal? I believe they both have the common ratios of 3.27, 3.55, and 3.73, the 9" being used for F250/F350, the 8" for F150. more info than that is above my paygrade.