4 speed conversion questions

There are several sellers on Ebay with surplus, low cost, racing drive-shafts. I bought an NOS, Southland Racing - NASCAR, 2.5" steel, shaft, (powder coated white for visibility), cut and welded to my request with Chrysler U-joints for under $200.. including shipping. Still holding up fine behind my 500 HP RB engine and 4-speed trans.