if your timing is good you can measure up when piston 1 is at TDC, and make the tool, before slacking off tension etc. i did this with my spare engine
my measurements were 88mm centre to centre of the dowels that go into the holes on cam sprockets, those dowels were 6mm, and their centres were 16mm up from the flat of the head where the jig sits. now these measurements are not taken from triumphs tool just my fabricated one