overdrive instal, one u-joint direct to Trans?

I have a brownie box overdrive I would like to put in a bobbed fire truck, I have limited space and was wondering if I could substitute the short (10") splined drive shaft and use one U-joint to connect directly to the back of the trans. I realize it would have to be lined up perfectly but I line up couplings on boats all the time to a few thousandths.

I little about the truck, 46 seagrave frame cut down 30", 4 very large cross members plus the engine helps stiffen the frame, motor is a GMC V12 about 600 lb/ft of torque, trans is a medium duty 5 spd from an international truck, rear is yet to be decided but likely a Sterling with 3.54:1, tires will be 40" commercial truck tires 11R 20 i think.

P.S. I realize I could just omit the overdrive all together, but I think its a cool thing to have. Thanks

 

I did that with a Hone overdrive (in 3 different vehicles), it always had a vibration....

 

Ya the more I thought about it the more i realized the thing really needs to flex side to side, up down and in out. Bottom line, it wont fit with u-joints and a slip joint so I omitted it instead of half assing it. Went with 3.08 gears 38" tires, the clark 5 spd has a wicked deep 1 1st anyway.