Asking for Advice Fix 273 or Replace

ENGINE IS 1967 273 SUPER COMMANDO OUT OF A BARRACUDA WAS REBUILT W/ NO DOCUMENTATION BEFORE I PURCHASED USED.....

This is how the paper work was stated when i got the car, so this is my problem, or question....

The car has been a great car except for a problem that has been driving me nuts over the last few months. There is now a lot of blow by, it burns about a qt. of oil about ever 500 miles. It realy doesnt smoke out of tail pipes but just a lot of blow by. The motor runs strong and I am happy with the motor beeing only a 273 and not a 340. The question is should I take the motor out and rebuild or replace the motor with a new crate motor. I never race it or get into it much and am happy if the motor stays the same meaning to keep the 273. I have the ability to remove the motor and do a rebuild but not sure on what to do.

So my question is kinda easy, should or would I be ok to rebuild or find out why it is has the problem or would you replace the motor.....

What would you guys do......??????

Thanks