Wheelbase unimportant if it's a blended-together frame, and track as stated is affected by wheel width/backspace. The most pertinent dimension would be, sitting at ride height with the lower a-arms parallel to the ground or nearly so, measure between the lower ball-joint centers.
Under same conditions with the wheels off (weight supported at the ball joints) you could also measure between the mounting surfaces on the discs, you would need to use a square or plumb-bob and make marks on the floor. If you go with that method (a little less precise) your width if it's a '70-'81 Camaro/Firebird (F-body), or '75-'79 Nova/Skylark/Seville etc. (X-body) should be about 63 1/2", but it's similar on the '68-'72 A's.
Really the most obvious peculiar feature of your frame is the details of the nub that sticks out from the bottom center of the crossmember, it's notably different among the various GM models...some are bigger, some little, some welded-on. You could just visually check that against the ones mentioned.