I agree that you should check for worn parts and replace them. As far as U-joints go, I have had good luck with the Brute Force line that is sold at Advance Auto--and I am not easy on them--I launch my 4 speed at 5K using slicks. I did upgrade to the 1330 series driveshaft and pinion yokes though. . . . . .
That's right, inside locks. The bigger ones have outside locks. Swapping the yoke and pinion flange (if you have a proper length shaft ready) might take a whole hour and a half if you stop for coffee. Go for it.