Driveshaft length using 1350 transmission and pinion yoke?

Gentlemen. Hope all is well. Need help determining custom driveshaft length. The car is a 68 Barracuda with A833 and 8 3/4. Factory length, if I'm correct, is 48.6 inches. Modifications from stock is the use of series 1350 transmission and rear end yokes. Question is, is the slip yoke at the transmission spaced off the rubber boot 3/4 - 1 inch. The output shaft is 3/16 inch below the end of rubber boot. Inserted the slip yoke compressing the boot but never bottomed out. With the slip yoke approx. 3/4 inch from end of rubber boot, centerline of u joints is approx 48.6 inches. This will be a custom made driveshaft so need to get this right. Thanks for any comments.20240916_110949[1].jpg