if the head gasket is not causing a problem, perhaps leave it alone,
however, since you are taking the engine out to do a re-seal,, now would be a great time to pull the head and do a cut on it to raise compression,, since the head is off, also a great time to pull the valves, do some minor porting and get a nice multi angle valve grind..
since you are pulling the timing cover to properly re seal the oil pan, also a great time to replace the timing chain,, with the timing chain off, also a great time to pull the cam, send it to Oregon Grinders for a re grind,,,
since the motor is out, great time to replace the water and fuel pumps, as well as the motor mounts...
and the list goes on..
may be best for you to get a firm $ amount that at this point in time you can stick in the motor.. ahead of the 4 bbl,, the best performance upgrade is to raise the compression,,
cc the head, measure piston recession, use an online calculator,, get then static up to 8.5, you will still run regular gas. Addressing the compression ratio is the best 1st performance move on a slant six.
for safety sake,, I would change out motor mounts and address any brake (front drums) issues next.