frame twister

[shaneo2112RUSH]

Just had a few questions if any one knows were to start on measuring the frame to see if its twisted, or out of alignment. i have a 68' chevy 1/2T C10 LWB

my wife noticed one day while driving behind the truck, that it looked like it was dog walking. and another time while tuning and tweaking after puting a SBC in. my daughter was helping me turn the engine on and off to get TDC(not the best thing to do but she was willing to learn!) while finaly getting it tuned and running. my daughter was acting like she was driving turning the steering wheel left to right(like we all did) and seen the front frame also moved from left to right near the radiator support. it moved about 1/8" . i dint know if the bolt were loose on the radiator support or the rivits were worn on the first crossmember support. or if its the way the frame flex from high pressure the tires and steering gear box make!

kind of stumped on what to do to fix this.. its my everyday driver but i guess if it come to the worst i might have to replace the frame.

after talking an ear off. sorry if you dont understand my problem. its been a long night with newborn and took about 1hr 1/2 to type and now its 10:00am been up since 12:00pm

thanks
shane v