3500# each - that is a good deal. Changing the axle width and modification for height isn't. Do you have 5 lug wheels? I don't on my '66 Overlander.
With the axle being 2 inches too wide (or long) that would be the deal killer in my opinon. I could live with the 10" brakes and make a mod for the height. Modifying the existing axle asembly to make it narrow means possible weakening the assembled unit. And if there is an issue you are gonna have to repace the axle(s) a second time. Really not fun and it could wreck a good vacation. Not to mention possible new (smaller and less capacity) wheels and tires.
For just a little more than double the price you could get units that are made for the job, correct angle, width and 12" brakes. Your time and effort are worth something.
1966 Mercury Park Lane 4 DR Breezeway 410 4V, C-6, 2.80 - Streamless.
1966 Lincoln 4 door Convertible 462 4V 1971 Ford LTD Convertible 429 4V Phoenix ~ Yeah it's hot however it's a dry heat!