8 3/4 disk breaks conversion

I Have A 72 A Body 8 3/4, I Want To Put Moser Large Pattern Axles And Willwood Disk Breaks But I Dont Know Which Axle To Run. The A Body Offset 2 1/4" Or The B-body Offset 2 1/2" To Make The Brakes Fit Right. Willwood Refered Me To There Web Site Which States A 2.38" Offset Moser Thinks I Need To Run The B-body Offset. Has Anybody Done This And Can You Tell Me What You Used. Its Going In A 73 Duster. Will My 14" Ralleys Fit