Don't have to do everything on day one.
If doing a rebuild do the best short block you can afford that's built around future plans.
Like a zero decked short block, if the top end is a little miss matched, it's ok it's only temporary, down the buy a set of good aftermarket heads etc.. as you go and can afford it. Or find a decent usable short block and spend money on top end.
I really like your thinking i think i will use what i have and use some kind of KB piston but i am a little lost on that should i use 399s or 167s if you dont know thats ok i will dig deeper into the internet