[bex316]

Thanks for the interesting post and pictures.
Just like you the Ace or Ace Bristol registrar from the AC Owners Club would be happy to be able to identify your Ace.
How do you know for sure it was originally Bristol and not AC powered?
Was it stated on the lost title?
The motor mounts might also give a clue but probably they were altered anyway to be able to fit the Ford 260. However, if you can include a picture of both these mounts, who knows they might still provide a lead.
The chassis, serial or VIN # should be stamped on the right hand motor mount but of course only if the original mount is still present.
Regarding the VIN #, it should also be stamped at least on the left hand trunk (boot) hinge (only the numbers, not the letters). This could be a 2, 3 or 4 digit number. The same number might also be stamped on the door hinge(s) and the left hand hood (bonnet) hinge. The door needs to be bare on the inside which it probably is given the current condition of the car.
I guess you have already looked in all these places and found no stamped numbers?

Jerry