Looking for some info/advice on a 71

[bmxbang]

Alright guys looking for some info on a 71 c10 i'm looking to purchase. It was originally a LWB truck but the frame has been shortened to a SWB. It currently has a 63 step side bed on it. Thats where my questions start? I would want to put a 68-72 fleet side bed on it. The current owner did not do the frame modifications and can't answer a lot about the frame or bed. The frame looks to be cut and reinforced correctly and the thing drives nice and straight but here is my question.

Whats the best way to figure out that it was cut correctly and to the correct measurements? does the 63 bed match up to the 68-72 wheelbase? I don't have a straight on side shot but this is the best I have. all the work on the truck looks really good and done correct. but its still nerving buying some one else's project.