If it was square on all four corners, the exact same measureemnt on the top and bottom on both sides I would try the .090 If it wasn't square, especially if wider on the bottom than the top, I would have the intake cut on a angle so the bottom is tighter than the top by .0015 to .0030 I've had to have that done many times on lots of Mopar V8 You might want to put the intake on the motor and then use seveal intake bolts(not real tight, maybe 20 to 30 inch lbs) to hold the manifold in place so you can get aggressive on using the feeler gauges to get it measure the best you can before proceeding You can loosen them and try moving the intake to get it center also before deciding what measurements are where We don't calll these motors Hemiriods for nuthin, if it was easy all of them would be perfect Good luck