I don't know the measurements of your frame, but a simple cross measuring will usually tell you an awful lot. Both sides aren't going to be bent exactly the same in an accident, most likely that is. Of course it's possible but usually one is different than the other. Here is a basic cross measuring plan.
Find "control points" that are the same on both sides. The frame is covered with them, very seldom is one side not the same as the other, it will be obvious, just look side to side and if there is a hole in the same spot on both sides chances are they are identical and usable control points.
Those A body frames are very similar all the way from 64-67 among all the makes, Buick, Olds, Pontiac and Chevy, you want to look at the frame ends closely to be sure they are the same as yours. Measure how long they are from control points around the suspension mounting to the over all length. In other words measure from say, the rear shock mount back to the rear of the frames crossmember to be sure it is exactly the same as yours. Do the same at the front. Take some photos of your front and rear frame horns where the bumper brackets bolt, take them with you. This is one area that changes among these frames.
When you do these measurements a little off isn't a big deal and a quarter inch difference is common with these old frames when they were new.
If you can put the frame on a level ground with jack stands under the "torque boxes" that being right at the front of where the fire wall mounts to the rear of the passenger compartment. With the frame sitting like this and you lay a level across the top of the jack stands and it's level you can then put the level across the front and rear of the frame horns and see if those are level to see if the frame is twisted. These are of course pretty basic checks and it would be nice to go crazy with a measurements off the floor and what but you need a REAL nice level floor and you probably won't find one where you get the frame. But if the jack stands are level and you get the frame on top of it at those points the level over the tops of the frame horns is going to do a decent job for you.