Driveshaft length question

The way i measured was from the metal end on the transmisson tail shaft (not the rubber seal area) you measure out to the rearend pumpkin yoke flange flat end. This is how the drive-line shop had me measure. Also i was a cheap *** the shop told me i needed a new front U-JOINT but i was like ehh sounds like bullshit..... Now i have been have a Slighht Vibration at 45000 RPMs lol wish i would of payed the extra 10 bucks lol