well...I am currently in the middle of an S-10 swap in a '51. We are using the frame from a '97 donor. It was a standard cab long box, the wheel base matched the 1/2 ton within 1/2 ". I have not fabricated body mounts yet (too cold) but here are the problems i can see so far. The up-sweep in the rear of the fram WILL cause interference with how the box will mount. I am certain the bed will need to be raised I should be able to keep it within an inch or two and do not see that affecting the appearance at all. The biggest problem I can see so far is the positioning of the engine. When placing the cab and fender on the original centerline of the wheel opening we discovered that the engine sat WAY too far forward. The water pump was well into where the 51's radiator needed to be. We plan to solve this problem bu mooving the cab forward to the proper place for the radiator fan (engine mounted) and modify the wheel openings rearward the same distance we move the cab forward. Hope this helps. BTW I have a 51 1/2T frame for sale