GWWirth,
Sorry to be a bit late to the conversation, but I think folks may be confused as your "title" asks about "Body differences between Big Bolts and 3/4 ton", but the actual question asks:
Do the 1947-1953 Cabs, Doors, Hood, Front Fenders and Grills interchange between 1 ton and 3/4 ton trucks.
To hopefully clarify the replies given, maybe this better explains the info:
Neither 1 ton or 3/4 ton trucks are considered "Big Bolts", so 1947-53 Cabs, Doors, Hood, Front Fenders and Grills DO interchange between those sized trucks (along with the same items on 1/2 ton trucks). "2ManyTrucks" notes the exception involving "bumpers" which is important to know for these sized trucks.
"Big Bolts" (1.5 ton and above trucks not including COEs) for 1947-53 do share the same "Cabs and Doors" of 1/2 ton thru 1 ton trucks, but DO NOT share "Hood, Front Fenders, Grills or Front Bumpers" (plus related under hood and fender parts) with the smaller 1 ton and below trucks. "Big Bolt" fender, hoods, grills, bumpers and related under sheet metal front end parts are larger sized to match the larger chassis and those will not fit 1 ton and below sized trucks.
If it might help visualize the differences, check out
this conversation I found with some pictures that may help see some of the differences.
Clear as mud???