You can’t use a 5.2 because the OP didn’t write it in his rules package. And I doubt I’d run the stock pistons and bores in one of those either. Factory machining was never better than decent.
I get what your saying, I'm just saying what I would do back in the day with my limited budget.
My budget has increased by a bunch since 1978 when I was 16. my cores back then were under 10 years old.
I acquired a 68 383 Roadrunner engine with less than 20,000 miles on it from a wrecked car.
I still have that engine and quite a few other big blocks.