79 GMC Sierra Driveshaft issues

[Turambar]

I've searched the forum for this, and I am sure this has come up before. For the life of me, I cant find it.

I dropped my 79 with DJM Suspension parts. I used a flip kit in the back. Specifically in the instructions, it states the following:

"Note : Two piece drive shafts on most 1/2 ton trucks should be replaced
with one piece drive shafts. If you must retain your two piece drive shaft,
modify the carrier bearing frame support so it can be raised approximately
1-1/2” to correct drive line angle."

I have a two piece drives shaft in my 1/2 truck. For giggles, I put everything back together stock. It was pretty obvious that this would not work. So, I painstakingly removed the carrier bearing frame support and shortened it be 1.5 inches. The truck isn't in ready to be fired up yet, but looking at it I am worried that the shaft isn't perfectly straight. So... I'm kinda worried...

Has anyone else done this? I am also considering this part of the DJM instructions: "Two piece drive shafts on most 1/2 ton trucks should be replaced with one piece drive shafts."

Total noob here. Where would I get said "one piece" driveshaft that would fit my truck? The end of my transmission (th400) and my diff both have a spot for u-joints to bolt up. How would the one piece drive shaft hook up? Could I get what I need from a salvage yard? What would I even be hunting?

I can probably provide pics tomorrow, but any advice would be appreciated.