406lawdawg
You have fallen into a common misunderstanding about the progression of models of the Chiefs Special. That being that the Model 36-1 replaced the Model 36. It didn't.
The Model 36-1, introduced in 1966, was a specific variant of the Chiefs Special. It had the 3" heavy barrel. From 1966 until 1988, the Model 36 and the Model 36-1 were produced concurrently. Eventually, in 1988, the Model 36-2 replaced the Model 36, and the Model 36-3 replaced the Model 36-1.
The J prefix was introduced in 1969, while both the Models 36 and 36-1 were still in production. Your example is from 1974, and it is a Model 36, as shown in the yoke cut.