Rear drum too big for wheel

I have a 70 RR that I am building. I just bought 15X10 Weld wheels and when I tried to install, the diameter of drum would not allow the wheel to slide on. The drums are 11 inch and interfere by about 1/2 inch diameter. Has anyone run into a similar problem? I have a 10 inch front drum from a previous car and it drops right in. I suppose I could try to find a 10 inch set-up but that won't be easy and I thought I'd ask here first.
Thanks,
Steve

An early 11" drum without the cooling fins would probably fit...

I have 15x10 Weld Pro Stars on my 65.It has a 69 runner rear with 11 in brakes.No problems.Rocky

I converted to 11 x 2 brakes on my Dart but running 15 x 7 Weld Pro Stars. No problems. Here is a pic of the drum.

According to the NAPA website, 11 inch front drums are 3/4 in. smaller O.D. than rears. I am going to give that a try.
Thank You

Front to rear likely won't interchange do to the offset built int the mounting surface of the drum... Not saying it won't but you need to check closely..