Of course anything we guess at here is just that, a guess, but multicarb setups, with progressive linkage and such, were always more troublesome than a single two barrel. I would assume that somebody disabled the secondary carbs for conveience.

An older motor manuel should give you some stamped engine codes identifying the horsepower rating and special options. All of the Chevy blocks were stamped on the top edge of the block, in front of the head. I would imagine the Olds would be similar.

BTW, A friend and I, in Illinois, put a J-2 in a glass Fiat coupe, just out of high school. It would have been about '66. It was a street rod, with slicks, and would pick up the front tires an inch or two on a good day!