I will say that those appear to be Speedway Engineering drive plate that are 24 spline. These are used with Grand National hubs with 2.5" bearings. The axles that we use in TT rear ends are either the big 40 spline (rarely used anymore) or 36 spline. Both of them will be too large in diameter to use in those drive plates. Also, TT axles won't fit through a 2.5" snout.
There is a small 40 axle. I have attached a resource that may help you.