1970 Blazer front disc conversion

[Nermal67]

I've got a complete front axle from a 1976 or 77 Blazer to convert my 1970 to front discs but the gears are a different ratio. I haven't pulled the knuckles off the two axles yet but they look like they might be interchangeable. The later model axle has the larger 3" tube and larger shafts. I'd rather not change the differential if I can help it. Assuming the knuckles will swap over, does anyone know if there is any reason I can't use the larger axle shafts from the 76 axle in the smaller tube 1970 axle housing? Thanks.