Finally had a bit of time so I got the numbers off the plate left hand side near the top handle.
967 05 27 00
991302315
Al
That should be a 55 Rancher made 1999 week 13, meaning it likely is a bit too early to have come with the closed port 45 mm top end.
According to the IPL, they came with the 46 mm open port at that point.
Is there a number in blue ink on top of the cylinder?
967 05 27 00 is the "part number" for the complete powerhead.