Yep, probably the same trilobe pin I replaced with a slight(!) mod to my lower mount for that very reason - where the trilobe holds the bottom main pin in - I through drilled & now use a HUGE split pin to hold that one in place.
Had to live with the tri-lobe up top as I'd have been thru' drilling the swivel bracket casting, and the other end would have ended up in the middle of the exhaust port! (mine is an older "pre sender" design- the big pin has a groove in the end that the tri-lobe engages in (hammered into the swiivel) to stop it falling out.
My plan is that I turn up a new top pin, drill the ram head & either grubscrew or split pin the main pin in place. Split pin preferable as it's a lot less likely to sieze.
Hence all my questions!