My opinion is that you really have to decide on the boat first. For drift fishing, these boats drift perfect. The cabins are like sails and I drift with the wind 85% of the time. If you're looking at the XLs and Mod Vs, the 250 is a great engine. If you're going to do regular trips of 50 to 60 miles off the Jersey Coast, I would suggest at minimum the XL, but preferably the Deep V. You have to look at years also. Many of the Parkers from the 90s had single engines (even deep Vs). Don't know if you're looking at new or used, but the specifications really differ from old to new. For example, my 1999 2530 DV only has a 154 gallon fuel tank, was only rated for 400 HP, and was only 5,000 pounds. It came from the factory with a 250 OX66. The new ones are about 800 pounds heavier, are rated for 500 HP, and have a minimum of 173 gallons of fuel.
I average about six offshore trips a year. The 250 OX66 pushed me along just fine. When I repowered with an F250 she was a little slower, but still moved along good. Not a rocket ship. But one thing I say often is, in this area (Jersey Coast), you can't cruise much faster than 25 mph in the ocean without beating the crap out of you or the boat.
But I have to admit, if I were doing it all over again, I'd go with Bryan's suggestion. For the safety with twins and power to fly with a fully loaded boat on those few calm days, I'd go with the Deep V and twin 200s.