When I bought my 50 ply coupe, the number on the title was the engine number. Not sure how they did things back then when there was an engine change.
When my little brother bought a 40 Dodge PU, he took the thing straight to the Oregon DMV and said he wanted to register it. It was all in one piece, but not a runner. They said bring it back when it is running. He said, You expect me to drop $10k into this then bring it back to see if I can get it registered? They ran the plate number, and came up empty handed. He had a title in the mail in the regular time. Blew me away!
My 38 is all CL and swapmeet parts gathered over about four years. I dread going to the DMV.