install a 1974 mustang 2 front end in a 1937 chev. truck

can some one tell me what degree i need to set the cross member on before i weld it in? thanks wayne  

I would contact an alignment shop, they can tell you what the caster angle should be and then you can work it out from there. Of course if your crossmember is stripped that might be difficult in which case try someone like Fatman Fabrication. Remember though to have the frame at the attitude that it will be when your ride is finished, when you set in the crossmember. Or at least know what it will be and compensate accordingly.
Good luck,
Scott  

With your frame at desired rake set your crossmember at 0 deg, cross check with a bubble level.
I built a 37 2 yrs ago and 38,000 mi,no probs at all !!!  

As I mention in my book, Hot Rod Body and Chassis Builder's Guide and agreeing with the previous posts, this is why it is critical to know (and preferably have on hand) the wheels and tires that you plan to use when the vehicle is finished when you are building the chassis (or installing a front crossmember). If the chassis is level and you install the crossmember level, and then put tall tires in the back, it puts the entire front end in a bind. So, the frame should sit at ride height (at the correct rake), with or without the wheels and tires installed, and then mount the crossmember at zero degrees. Some installations will require the crossmember to be installed at 1 to 2 degrees, which will increase caster, but since Rustynuts1 has one of these trucks, I would go with his suggestion of zero. Just remember that zero is with the entire chassis at the desire rake.

Dennis