My truck is licensed as a 75' but my buddy said the frame might be a 78/79 since it has a 78/79 steering box and he said that box will not bolt into a 75. How do check to see if the cab and frame are a match?

 

On the top of the right frame rail, right under the front of the cab(or just a bit forward) the VIN number is stamped into the frame. Besides the VIN on the door, there may be a metal tag screwed to the front of the in the engine compartment and also a metal tag attached to the bed, underneath, center, front. Hope this helps.