I have a homemade vertical splitter that has a trunnion cylinder on it. It is a very heavy built surplus cylinder that I would say was for like a track Cat type loader or something like that. It has last well the last ten years. I think trying to weld mounts on a base mount cylinder is not going to last. The reason I built the splitter around a trunnion cylinder was the cost of the cylinder back then.
Trunnion cylinders that have a band welded to the tube have the hone work done afterward welding, it will have a misshapen ID due to heat. And like was said above the wall thickness is considerably more on tube mounted trunnions.
Tie-rod cylinders are the easy to convert just a front plate and replace the existing rods with longer ones. I use 3/4 inch higher strength rods from McMaster-Carr