I'm hoping to get a definitive answer from the current owner of this car, if he responds to my email, as I know he is in possession of the details of its history.
I've now had a very helpful reply from the current owner of this car, BEX 148, which I can do no better than quote below to resolve all the questions regarding this car:
QUOTE
The car is a part of the first batch (of seven) Ace-Bristols shipped to the Venezuelan importer Juan 'Jack' Fernandez. All took to the race track.
Three of them were modified by a Caracas-based German artisan, Karl Pentz, in 1956. All were different, but Pentz clearly took his styling cues from the plethora of privateer sports racing Ferraris and Maseratis that filled the grids at the time.
BEX 148 belonged to Oscar Lupi, BEX 149 to Antonio Izquierdo and the third car belonged to Renny Ottolina; I'm not certain of the chassis number.
Alas, I know the Ottolina car was broken up, and I fear the same may have happened to BEX 149. The cars were very hard used on poor roads and there was little incentive in the 1960s to preserve worn out no longer competitive racing cars.
UNQUOTE
So the modifier was indeed Karl Pentz as suggested by ropat53, and I think the answer to the 'make of car' question should really still be AC and as the question of who modified the body was not part of the original question this puzzle was really answered in my Reply #43 on 4th June! Clearly CADV could never been construed as the make!