If you find the gear ratios very low have you thought of changing the rear axle to a higher ratio?
According to my workshop manual the +4 with the Vanguard engine had a 4.1 or 3.73 Salisbury. Not sure of the availability on crown wheel and pinions for your axle but it would have the advantage of keeping it standard and retaining value.
Moss box cars fetch a premium over here.
