What chassis do I have?

[Sevens]

I have a 1965 GMC 3/4 ton truck...that's what the VIN number tells me anyway...

At some point in its lifetime, someone did a 5 lug swap and drivetrain swap; it has leaf-springs in the rear. I believe everything that was swapped was from a 1975 C10 (based on casting numbers and the PO's story).

I plan on lowering the rear-end a few inches.

I don't want to buy parts and see if they fit only to find out that they are wrong.


My question is this; is there a difference between a 1965 chassis and a 1975 chassis...and if so, how can I tell which one mine is?