Pinion angle help.

I'm a tempting to set pinion angle on my 70 Duster. Any help/ advice would be greatly appreciated. It was a 318 with 904 trans and 7 1/4 rear. I put in a 360 and a 8 3/4 rear. It still has 904 tranny. I just took angle off tailshaft and it is. 1 degree down. What should the pinion angle be. The rear end don't have perches , so I will be weilding them on after I set the correct angle. Thanks in advance.