Some times you just need to talk to someone. My 51 Plymouth has a title that uses the engine serial number not the vehicle serial number, TX law for pre 55's, except Fords. I have the original engine that matches that number in the car.

However, I am building a warmed up 230 from a 52 Dodge to put in the 51. The engine serial number will now no longer match and that is supposed to be checked every year during the safety inspection. So when I renewed my registration this past August I asked the clerk, she wasn't sure so she went to ask for help. A few minutes later the County Tax Assessor (that is who handle this kind of stuff here) herself came out with the paperwork and information I needed.

Due to the peculiarities of Texas law in this regard, I can get a new title with the new engine serial number on it but if I ever want to put the original back in I have to retitle it.

Or I can play swap the engines every year to get it inspected then swap back.

Or I can get antique plates and do the swap after that, which means no more yearly inspections but limitations on when and how I can enjoy my car.