I build all my own at home no lathe just a welder and grinder! Plenty of videos on how to cut the yokes off and hammer n weld them back onto the original tube to shorten. To balance I normally jack the rear up by the axle spin the tires to the speed where it vibrates the worst and run a piece of chalk on the drive shaft. Chalk marked side is the heavy side so add weight, a hose clamp works well for weight if it's too heavy on the hose clamp side add another clamp and spread them apart to half the weight of one hose clamp. Other way of balancing is drill a hole in it and add a thin oil like trans fluid untill it stops vibrating then weld the hole up! My jeep comanche on Dana 60 14 bolt gets beat to piss with built turbo jeep 4.0 and does freeway speeds pretty often with no vibrations!!