I just ordered & received my 35 spline axles from Strange a couple months ago for my Cougar project. I'm using a Mustang 9" rear end that has been braced and spring perches boxed and has the small bearing 2-3/4" ends. It was no problem having them made with the small bearing, but most people seem to like the larger bearing ends. Probably make sure your choice of brakes is going to work with the small bearing too. You're ordering a good aftermarket case, so it shouldn't be a problem, but usually you need the 3.25" bearing 9" case to work with 35 spline spool, but Mark Williams makes a special spool/bearing that will work with the 3.06" bearing case. If you're not using a spool make sure your choice of differential will work. In your instance probably be sure to get the 3.25" case. Other downside would be 35 spline axles will weigh more than 31, but you could get them gun drilled to lighten for a strict drag race application. I talked to all the major axle companies at PRI, the only company that felt confident their gun drilled 35 spline axles would hold up to street use ( I plan on Dragweek) was Mark Williams. In the end I just went with Strange and skipped the gun drilling. I had Strange drill my axles for all three wheel bolt patterns, mostly to save a little more weight, and although their website lists an extra charge, they did not charge extra. Maybe I just got lucky. The extra holes also give you access to the retaining nuts. There are other things they can do to save weight, but it will depend on what you intend to do.