15x10 with 3.5" backspacing?

[Silver Square]

I'm thinking about getting some new 15x10 US Mag Indys for my '77 K15. 4" BDS lift, 35x12.50 tires are being used. These seem to only be available with 3.5" of backspacing. Does anybody know if that will work OK?

 

[bucket]

They will rub unless you trim the lower fenders some.

 

[Silver Square]

Looks like I can get them in 15x9 with 4.5" BS... would that be any better?