Well I do have a passenger side dip stick. And I have 100% two piece rear main because I replaced it about a year ago!
Helpful to read this, thanks. My truck is registered as a 1973 from the VIN on the door post, but the PO swapped in a dash and transmission and engine from an 81 Suburban. I had been wondering why things were not matching up with the '73 diagrams and service manual. The pass side dipstick in particular made me feel like a weird deformed freak who should hide in shame. Now I understand.
(Had I figured this all out when I found the 81 VIN under the dash cover, I might have saved myself much mental anguish and obsessive worry.)