Air Ride Driveshaft Ques..

[bguild]

I have a 1968 SWB Truck.. I have it down to the frame and i plan to put a step notch in the rear very soon. I am close to being able to bolt the cab back on but I have some questions regarding the driveshaft. i currently plan to run 22's in the rear and 20's up front and put some bags all the way around. I know ideally I should put a double driveshaft or a 2-piece whatever you call them. I want to see how low i can go with keeping the stock driveshaft and just modifying the current crossmember. If I put a new driveshaft loop in how much taller do I need to go? I dont mind tunnel the floor some if i need to but would rather not. I know i could buy a cpp crossmember for around 200 bucks but since i will be welding stuff in the rear I figure i would save some money and just weld in a new driveshaft loop.

Any help would be appreciated--pictures-- concerns withdoing it this way-- really anything because i am new to the air ride scene.
Thanks in advance.