From reading your other post I gather your new tank is not already drilled. Do some research on the DIY forums and ask alot of questions. There are pro's and con's to each. I my opionion, if you want a drilled tank, it is best to buy it already drilled from the company.
Down side of drilling your own tank, you have a 50/50 chance of cracking the glass and ruining the tank. Unless you buy brand new diamond tipped hole bits your chances of cracking your tank go up to 70/30. And if you never drilled a tank before, 80/20. I know a 140 is too big to drag all over the place, but maybe see if your LFS might drill the holes for you. But even if the hole drilling seems to go smoothly, and you don't think you've cracked your tank, inspect the hole very closely. Use a magnifying glass if you need to. Some times it will look like the hole is fine, but there are very small hair line crack right on the edge of the hole, once you fill your tank the stress will make them worse and eventually give way. You don't want your tank full and it just blow out. That is why I say buy it from the factory drilled.
You could use an over flow box as was suggested to you. You just need to make sure you check it regularly and don't get anything clogged up in it. A lot of people don't like overflow boxes, to many people have woke up in the morning to find their livingroom flooded. So research both ways, and know the draw back for each. Then you can make an informed choice.