I took the frame off my 1970 442, the rear alignment is off by about half a inch give or take due to probably some accident in the past, am i gonna have any problems with it being off that much?

There is a small crack and some lower rail wavy bends that need straightening as well all in the rear nothing that look too bad from my eye.

 

Take it to a good frame shop for an assessment.

 

Your frame needs to be repaired and it will need to go to a good shop that works on these cars. Some no longer have the parts to tie the frame down to a frame rack. So ask to be sure.

Unfortunately for you, you will need to put the body back on the frame before you get it straightened/repaired. If the rear frame body mount locations move, and they likely will if your frame is off by1/2" +/- you run the risk of not being able to get the body to fit the straightened frame since the truck pan likely moved when the frame did. Best to bolt the body back on and have the frame and body all pulled at the same time. Otherwise you're inviting bigger problems.

 

The body might not have moved, as it is a pretty rigid structure. Look closely to see if it has wrinkles sheet metal, etc. Also, if the body mount bolts were offset in some of the frame holes, then the body might have stayed straight while the frame was distorted. 1/2" isn't that much; the body mount holes in the frame are big.