Nomura's hitting as a catcher

While the data I have doesn't break down according to home runs hit by position, I can provide games played at other positions per year with the home runs.

Year  Games   HRs  Games per Position
----  -----  ----  ------------------------------
1954      9     0  C:   8
1955      0     -  ------
1956    129     7  C: 127
1957    132*   30* C: 132
1958    120    21  C: 120
1959    132    21  C: 131
1960    124    29  C: 121
1961    136    29* C: 133  1B: 1
1962    133*   44* C: 130  1B: 4  OF: 2
1963    150*   52* C: 150
1964    148    41* C: 148
1965    136    42* C: 133
1966    133*   34* C: 133
1967    133*   35* C: 133
1968    133    38* C: 133
1969    106    22  C: 104
1970    130*   42  C: 130
1971    127    29  C: 128  1B: 1  OF: 1
1972    129    35  C: 129
1973    129    28  C: 129
1974     83    12  C:  75
1975    129    28  C: 125  DH:  5
1976    119    10  C: 113  DH:  6
1977    127    16  C: 127
1978     64     3  C:  31  DH: 20
1979     74     5  C:  59
1980     52     4  C:  41  DH:  1
===== =====  ====  ==============================
Total 3,017   657  C: 2,921  1B: 6  OF: 3  DH: 32

* Denotes league leader.

As you can see, he was overwhelmingly working as a catcher throughout his career. I imagine you can work out the number of pinch hits by subtracting games per position from games played, however, he may have played multiple positions in a single game (getting counted twice), and may have appeared in games as a pinch runner (unlikely - but possible), so any such number would have a margin of error.

I'm afraid that this is as close as I can get to answering your question.

So Mike Piazza only has a few hundred home runs or so to go at least before he's the all-time, all-world leader. And I also had no idea Nomura played for so long.

Thanks for finding the stats!