I have two of the 2.5" truck manifolds. One came from a early '70s truck, the other was a new replacement I got off e-bay. I bought the replacement to create a split manifold for my '37 and it may be usefull in a turbo application for the same reasons I bought it. The exhaust outlet sits under cylinder #s 4&5 instead of under the carb flange, and it points pretty much straight down. There is a big flat area under the # 2&3 cylinders that allowed me to build a symetrical split manifold. The 292 manifold besides having the rearward sited outlet, is flat under the carbflange going forward until under the 2-3 cylinders, and it has reinforcement "fins" front and rear.
Having the outlet under 4&5 gives more distance to wrangle the exhaust pipe and the straight down, rather than pointed rearward, doesn't hurt either if you are using one for a turbo placed as in the photos above in this thread.
