440 engine rebuild.

[1969CoronetR/T]

My engine builder took off my heads to put on the set of ported Indy EZ heads and noticed oil pooling on top of the pistons. He suggested a .030 overbore and I have noticed it does not have the power that it once had five years ago. It has a lot of blowby and would coat my TTI headers and valve covers with oil. My question is this: Would a 'tired' engine need rebuilt or bored out if I never saw a puff of smoke come out of the tailpipes?
Thanks

 

[GTX MATT]

Its possible that it could be tired and not burning tons of oil, yes.