I'm using the term "freshen" to mean a general rebuild to make sure everything is in good shape..whatever is needed. At least rings, bearings, oil pump. In your case it will most likely need to be bored since you've got quite a few hours on it. Of course it would be best to do it right by zero decking the block, blueprinting everything, etc. Depends on your budget. I wouldn't change cams and do head work, etc. without doing the short block with over 400 hrs. on it. Generally I've found engines with that many hours to have an unacceptable amount of taper in the cylinders to allow re-ringing without boring.

Thanks Bob.

Would it be more cost effective to rebuild or to purchase a short block?

You've got a good engine. Just rebuild it and put your money in the cylinder heads. That's where the HP is. Either have yours ported or get an aftermarket set. If you can afford it, upgrade to a hydraulic roller cam also. Building it into a 540 will gain some low end torque, but not really much HP. So, unless you have to buy a new crank anyway it wouldn't be worth it.